diff --git a/mozilla/layout/base/public/nsHTMLReflowMetrics.h b/mozilla/layout/base/public/nsHTMLReflowMetrics.h
index 46b0f201003..4ad294a1681 100644
--- a/mozilla/layout/base/public/nsHTMLReflowMetrics.h
+++ b/mozilla/layout/base/public/nsHTMLReflowMetrics.h
@@ -187,7 +187,21 @@ struct nsHTMLReflowMetrics {
     width = height = 0;
     ascent = descent = 0;
   }
-  
+
+ /**
+  * set the maxElementWidth to the desired width. If the frame has a percent
+  * width specification it can be shrinked to 0 if the containing frame shrinks
+  * so we need to report 0 otherwise the incr. reflow will fail
+  * @param aWidthUnit - the width unit from the corresponding reflowstate
+  */
+  void nsHTMLReflowMetrics::SetMEWToActualWidth(nsStyleUnit aWidthUnit) {
+    if (aWidthUnit != eStyleUnit_Percent) {
+      mMaxElementWidth = width;
+    } else {
+      mMaxElementWidth = 0;
+    }
+  }
+
   nsHTMLReflowMetrics& operator=(const nsHTMLReflowMetrics& aOther)
   {
     mMaxElementWidth = aOther.mMaxElementWidth;
diff --git a/mozilla/layout/forms/nsComboboxControlFrame.cpp b/mozilla/layout/forms/nsComboboxControlFrame.cpp
index 360ad1cd101..4ffff02f002 100644
--- a/mozilla/layout/forms/nsComboboxControlFrame.cpp
+++ b/mozilla/layout/forms/nsComboboxControlFrame.cpp
@@ -1038,7 +1038,7 @@ nsComboboxControlFrame::ReflowCombobox(nsPresContext *         aPresContext,
   REFLOW_NOISY_MSG3("**AdjustCombobox - Reflow: WW: %d  HH: %d\n", aDesiredSize.width, aDesiredSize.height);
 
   if (aDesiredSize.mComputeMEW) {
-    aDesiredSize.mMaxElementWidth = aDesiredSize.width;
+    aDesiredSize.SetMEWToActualWidth(aReflowState.mStylePosition->mWidth.GetUnit());
   }
 
   aDesiredSize.ascent =
@@ -1549,7 +1549,7 @@ nsComboboxControlFrame::Reflow(nsPresContext*          aPresContext,
 
   // Set the max element size to be the same as the desired element size.
   if (aDesiredSize.mComputeMEW) {
-    aDesiredSize.mMaxElementWidth = aDesiredSize.width;
+    aDesiredSize.SetMEWToActualWidth(aReflowState.mStylePosition->mWidth.GetUnit());
   }
 
 #if 0
@@ -1590,6 +1590,7 @@ nsComboboxControlFrame::Reflow(nsPresContext*          aPresContext,
   aDesiredSize.mOverflowArea.width  = aDesiredSize.width;
   aDesiredSize.mOverflowArea.height = aDesiredSize.height;
 
+  FinishAndStoreOverflow(&aDesiredSize);
   NS_FRAME_SET_TRUNCATION(aStatus, aReflowState, aDesiredSize);
   return rv;
 
diff --git a/mozilla/layout/forms/nsFieldSetFrame.cpp b/mozilla/layout/forms/nsFieldSetFrame.cpp
index 0ed1a7484a1..8a98676ab64 100644
--- a/mozilla/layout/forms/nsFieldSetFrame.cpp
+++ b/mozilla/layout/forms/nsFieldSetFrame.cpp
@@ -593,12 +593,12 @@ nsFieldSetFrame::Reflow(nsPresContext*          aPresContext,
     aDesiredSize.descent = 0;
     aDesiredSize.mMaximumWidth = aDesiredSize.width;
     if (aDesiredSize.mComputeMEW) {
-        // if the legend is wider use it
-        if (aDesiredSize.mMaxElementWidth < mLegendRect.width)
-            aDesiredSize.mMaxElementWidth = mLegendRect.width;
+        aDesiredSize.SetMEWToActualWidth(aReflowState.mStylePosition->mWidth.GetUnit());
+
+        // if the legend is wider use it
+        if (aDesiredSize.mMaxElementWidth < mLegendRect.width + borderPadding.left + borderPadding.right)
+            aDesiredSize.mMaxElementWidth = mLegendRect.width + borderPadding.left + borderPadding.right;
 
-        // add in padding.
-        aDesiredSize.mMaxElementWidth += borderPadding.left + borderPadding.right;
     }
     aDesiredSize.mOverflowArea = nsRect(0, 0, aDesiredSize.width, aDesiredSize.height);
     if (mLegendFrame)
diff --git a/mozilla/layout/forms/nsFileControlFrame.cpp b/mozilla/layout/forms/nsFileControlFrame.cpp
index cad3beaacda..0f12db664f6 100644
--- a/mozilla/layout/forms/nsFileControlFrame.cpp
+++ b/mozilla/layout/forms/nsFileControlFrame.cpp
@@ -441,6 +441,9 @@ NS_IMETHODIMP nsFileControlFrame::Reflow(nsPresContext*          aPresContext,
           txtRect.height = aDesiredSize.height;
           mTextFrame->SetRect(txtRect);
         }
+        if (aDesiredSize.mComputeMEW) {
+           aDesiredSize.SetMEWToActualWidth(aReflowState.mStylePosition->mWidth.GetUnit());
+        }
       }
 
       // Do RTL positioning
diff --git a/mozilla/layout/forms/nsFormControlFrame.cpp b/mozilla/layout/forms/nsFormControlFrame.cpp
index aef97c0373e..c7ffea01a17 100644
--- a/mozilla/layout/forms/nsFormControlFrame.cpp
+++ b/mozilla/layout/forms/nsFormControlFrame.cpp
@@ -470,7 +470,7 @@ nsFormControlFrame::GetDesiredSize(nsPresContext*          aPresContext,
   aDesiredLayoutSize.ascent = aDesiredLayoutSize.height;
   aDesiredLayoutSize.descent = 0;
   if (aDesiredLayoutSize.mComputeMEW) {
-    aDesiredLayoutSize.mMaxElementWidth = aDesiredLayoutSize.width;
+    aDesiredLayoutSize.SetMEWToActualWidth(aReflowState.mStylePosition->mWidth.GetUnit());
   }
   aDesiredWidgetSize.width  = aDesiredLayoutSize.width;
   aDesiredWidgetSize.height = aDesiredLayoutSize.height;
diff --git a/mozilla/layout/forms/nsHTMLButtonControlFrame.cpp b/mozilla/layout/forms/nsHTMLButtonControlFrame.cpp
index 3349173cddd..8e014762484 100644
--- a/mozilla/layout/forms/nsHTMLButtonControlFrame.cpp
+++ b/mozilla/layout/forms/nsHTMLButtonControlFrame.cpp
@@ -460,7 +460,7 @@ nsHTMLButtonControlFrame::Reflow(nsPresContext* aPresContext,
   //aDesiredSize.height += aReflowState.mComputedBorderPadding.top + aReflowState.mComputedBorderPadding.bottom;
 
   if (aDesiredSize.mComputeMEW) {
-    aDesiredSize.mMaxElementWidth = aDesiredSize.width;
+    aDesiredSize.SetMEWToActualWidth(aReflowState.mStylePosition->mWidth.GetUnit());
   }
 
   // Make sure we obey min/max-width and min/max-height
diff --git a/mozilla/layout/forms/nsIsIndexFrame.cpp b/mozilla/layout/forms/nsIsIndexFrame.cpp
index b401acf7603..104551a4bbf 100644
--- a/mozilla/layout/forms/nsIsIndexFrame.cpp
+++ b/mozilla/layout/forms/nsIsIndexFrame.cpp
@@ -315,6 +315,9 @@ NS_IMETHODIMP nsIsIndexFrame::Reflow(nsPresContext*          aPresContext,
   // The Areaframe takes care of all our reflow 
   // (except for when style is used to change its size?)
   nsresult rv = nsAreaFrame::Reflow(aPresContext, aDesiredSize, aReflowState, aStatus);
+  if (aDesiredSize.mComputeMEW) {
+    aDesiredSize.SetMEWToActualWidth(aReflowState.mStylePosition->mWidth.GetUnit());
+  }
   NS_FRAME_SET_TRUNCATION(aStatus, aReflowState, aDesiredSize);
   return rv;
 }
diff --git a/mozilla/layout/generic/nsHTMLReflowMetrics.h b/mozilla/layout/generic/nsHTMLReflowMetrics.h
index 46b0f201003..4ad294a1681 100644
--- a/mozilla/layout/generic/nsHTMLReflowMetrics.h
+++ b/mozilla/layout/generic/nsHTMLReflowMetrics.h
@@ -187,7 +187,21 @@ struct nsHTMLReflowMetrics {
     width = height = 0;
     ascent = descent = 0;
   }
-  
+
+ /**
+  * set the maxElementWidth to the desired width. If the frame has a percent
+  * width specification it can be shrinked to 0 if the containing frame shrinks
+  * so we need to report 0 otherwise the incr. reflow will fail
+  * @param aWidthUnit - the width unit from the corresponding reflowstate
+  */
+  void nsHTMLReflowMetrics::SetMEWToActualWidth(nsStyleUnit aWidthUnit) {
+    if (aWidthUnit != eStyleUnit_Percent) {
+      mMaxElementWidth = width;
+    } else {
+      mMaxElementWidth = 0;
+    }
+  }
+
   nsHTMLReflowMetrics& operator=(const nsHTMLReflowMetrics& aOther)
   {
     mMaxElementWidth = aOther.mMaxElementWidth;
diff --git a/mozilla/layout/generic/nsLeafFrame.cpp b/mozilla/layout/generic/nsLeafFrame.cpp
index da5f7649c12..2434b5a090c 100644
--- a/mozilla/layout/generic/nsLeafFrame.cpp
+++ b/mozilla/layout/generic/nsLeafFrame.cpp
@@ -81,7 +81,7 @@ nsLeafFrame::Reflow(nsPresContext* aPresContext,
   nsMargin borderPadding;
   AddBordersAndPadding(aPresContext, aReflowState, aMetrics, borderPadding);
   if (aMetrics.mComputeMEW) {
-    aMetrics.mMaxElementWidth = aMetrics.width;
+    aMetrics.SetMEWToActualWidth(aReflowState.mStylePosition->mWidth.GetUnit());
   }
   aStatus = NS_FRAME_COMPLETE;
 
diff --git a/mozilla/layout/generic/nsSpacerFrame.cpp b/mozilla/layout/generic/nsSpacerFrame.cpp
index 22748a50684..4532c6f91cc 100644
--- a/mozilla/layout/generic/nsSpacerFrame.cpp
+++ b/mozilla/layout/generic/nsSpacerFrame.cpp
@@ -159,7 +159,7 @@ SpacerFrame::Reflow(nsPresContext*          aPresContext,
   }
 
   if (aMetrics.mComputeMEW) {
-    aMetrics.mMaxElementWidth = aMetrics.width;
+    aMetrics.SetMEWToActualWidth(aReflowState.mStylePosition->mWidth.GetUnit());
   }
 
   NS_FRAME_SET_TRUNCATION(aStatus, aReflowState, aMetrics);
diff --git a/mozilla/layout/html/base/src/nsLeafFrame.cpp b/mozilla/layout/html/base/src/nsLeafFrame.cpp
index da5f7649c12..2434b5a090c 100644
--- a/mozilla/layout/html/base/src/nsLeafFrame.cpp
+++ b/mozilla/layout/html/base/src/nsLeafFrame.cpp
@@ -81,7 +81,7 @@ nsLeafFrame::Reflow(nsPresContext* aPresContext,
   nsMargin borderPadding;
   AddBordersAndPadding(aPresContext, aReflowState, aMetrics, borderPadding);
   if (aMetrics.mComputeMEW) {
-    aMetrics.mMaxElementWidth = aMetrics.width;
+    aMetrics.SetMEWToActualWidth(aReflowState.mStylePosition->mWidth.GetUnit());
   }
   aStatus = NS_FRAME_COMPLETE;
 
diff --git a/mozilla/layout/html/base/src/nsSpacerFrame.cpp b/mozilla/layout/html/base/src/nsSpacerFrame.cpp
index 22748a50684..4532c6f91cc 100644
--- a/mozilla/layout/html/base/src/nsSpacerFrame.cpp
+++ b/mozilla/layout/html/base/src/nsSpacerFrame.cpp
@@ -159,7 +159,7 @@ SpacerFrame::Reflow(nsPresContext*          aPresContext,
   }
 
   if (aMetrics.mComputeMEW) {
-    aMetrics.mMaxElementWidth = aMetrics.width;
+    aMetrics.SetMEWToActualWidth(aReflowState.mStylePosition->mWidth.GetUnit());
   }
 
   NS_FRAME_SET_TRUNCATION(aStatus, aReflowState, aMetrics);
diff --git a/mozilla/layout/html/forms/src/nsComboboxControlFrame.cpp b/mozilla/layout/html/forms/src/nsComboboxControlFrame.cpp
index 360ad1cd101..4ffff02f002 100644
--- a/mozilla/layout/html/forms/src/nsComboboxControlFrame.cpp
+++ b/mozilla/layout/html/forms/src/nsComboboxControlFrame.cpp
@@ -1038,7 +1038,7 @@ nsComboboxControlFrame::ReflowCombobox(nsPresContext *         aPresContext,
   REFLOW_NOISY_MSG3("**AdjustCombobox - Reflow: WW: %d  HH: %d\n", aDesiredSize.width, aDesiredSize.height);
 
   if (aDesiredSize.mComputeMEW) {
-    aDesiredSize.mMaxElementWidth = aDesiredSize.width;
+    aDesiredSize.SetMEWToActualWidth(aReflowState.mStylePosition->mWidth.GetUnit());
   }
 
   aDesiredSize.ascent =
@@ -1549,7 +1549,7 @@ nsComboboxControlFrame::Reflow(nsPresContext*          aPresContext,
 
   // Set the max element size to be the same as the desired element size.
   if (aDesiredSize.mComputeMEW) {
-    aDesiredSize.mMaxElementWidth = aDesiredSize.width;
+    aDesiredSize.SetMEWToActualWidth(aReflowState.mStylePosition->mWidth.GetUnit());
   }
 
 #if 0
@@ -1590,6 +1590,7 @@ nsComboboxControlFrame::Reflow(nsPresContext*          aPresContext,
   aDesiredSize.mOverflowArea.width  = aDesiredSize.width;
   aDesiredSize.mOverflowArea.height = aDesiredSize.height;
 
+  FinishAndStoreOverflow(&aDesiredSize);
   NS_FRAME_SET_TRUNCATION(aStatus, aReflowState, aDesiredSize);
   return rv;
 
diff --git a/mozilla/layout/html/forms/src/nsFieldSetFrame.cpp b/mozilla/layout/html/forms/src/nsFieldSetFrame.cpp
index 0ed1a7484a1..8a98676ab64 100644
--- a/mozilla/layout/html/forms/src/nsFieldSetFrame.cpp
+++ b/mozilla/layout/html/forms/src/nsFieldSetFrame.cpp
@@ -593,12 +593,12 @@ nsFieldSetFrame::Reflow(nsPresContext*          aPresContext,
     aDesiredSize.descent = 0;
     aDesiredSize.mMaximumWidth = aDesiredSize.width;
     if (aDesiredSize.mComputeMEW) {
-        // if the legend is wider use it
-        if (aDesiredSize.mMaxElementWidth < mLegendRect.width)
-            aDesiredSize.mMaxElementWidth = mLegendRect.width;
+        aDesiredSize.SetMEWToActualWidth(aReflowState.mStylePosition->mWidth.GetUnit());
+
+        // if the legend is wider use it
+        if (aDesiredSize.mMaxElementWidth < mLegendRect.width + borderPadding.left + borderPadding.right)
+            aDesiredSize.mMaxElementWidth = mLegendRect.width + borderPadding.left + borderPadding.right;
 
-        // add in padding.
-        aDesiredSize.mMaxElementWidth += borderPadding.left + borderPadding.right;
     }
     aDesiredSize.mOverflowArea = nsRect(0, 0, aDesiredSize.width, aDesiredSize.height);
     if (mLegendFrame)
diff --git a/mozilla/layout/html/forms/src/nsFileControlFrame.cpp b/mozilla/layout/html/forms/src/nsFileControlFrame.cpp
index cad3beaacda..0f12db664f6 100644
--- a/mozilla/layout/html/forms/src/nsFileControlFrame.cpp
+++ b/mozilla/layout/html/forms/src/nsFileControlFrame.cpp
@@ -441,6 +441,9 @@ NS_IMETHODIMP nsFileControlFrame::Reflow(nsPresContext*          aPresContext,
           txtRect.height = aDesiredSize.height;
           mTextFrame->SetRect(txtRect);
         }
+        if (aDesiredSize.mComputeMEW) {
+           aDesiredSize.SetMEWToActualWidth(aReflowState.mStylePosition->mWidth.GetUnit());
+        }
       }
 
       // Do RTL positioning
diff --git a/mozilla/layout/html/forms/src/nsFormControlFrame.cpp b/mozilla/layout/html/forms/src/nsFormControlFrame.cpp
index aef97c0373e..c7ffea01a17 100644
--- a/mozilla/layout/html/forms/src/nsFormControlFrame.cpp
+++ b/mozilla/layout/html/forms/src/nsFormControlFrame.cpp
@@ -470,7 +470,7 @@ nsFormControlFrame::GetDesiredSize(nsPresContext*          aPresContext,
   aDesiredLayoutSize.ascent = aDesiredLayoutSize.height;
   aDesiredLayoutSize.descent = 0;
   if (aDesiredLayoutSize.mComputeMEW) {
-    aDesiredLayoutSize.mMaxElementWidth = aDesiredLayoutSize.width;
+    aDesiredLayoutSize.SetMEWToActualWidth(aReflowState.mStylePosition->mWidth.GetUnit());
   }
   aDesiredWidgetSize.width  = aDesiredLayoutSize.width;
   aDesiredWidgetSize.height = aDesiredLayoutSize.height;
diff --git a/mozilla/layout/html/forms/src/nsHTMLButtonControlFrame.cpp b/mozilla/layout/html/forms/src/nsHTMLButtonControlFrame.cpp
index 3349173cddd..8e014762484 100644
--- a/mozilla/layout/html/forms/src/nsHTMLButtonControlFrame.cpp
+++ b/mozilla/layout/html/forms/src/nsHTMLButtonControlFrame.cpp
@@ -460,7 +460,7 @@ nsHTMLButtonControlFrame::Reflow(nsPresContext* aPresContext,
   //aDesiredSize.height += aReflowState.mComputedBorderPadding.top + aReflowState.mComputedBorderPadding.bottom;
 
   if (aDesiredSize.mComputeMEW) {
-    aDesiredSize.mMaxElementWidth = aDesiredSize.width;
+    aDesiredSize.SetMEWToActualWidth(aReflowState.mStylePosition->mWidth.GetUnit());
   }
 
   // Make sure we obey min/max-width and min/max-height
diff --git a/mozilla/layout/html/forms/src/nsIsIndexFrame.cpp b/mozilla/layout/html/forms/src/nsIsIndexFrame.cpp
index b401acf7603..104551a4bbf 100644
--- a/mozilla/layout/html/forms/src/nsIsIndexFrame.cpp
+++ b/mozilla/layout/html/forms/src/nsIsIndexFrame.cpp
@@ -315,6 +315,9 @@ NS_IMETHODIMP nsIsIndexFrame::Reflow(nsPresContext*          aPresContext,
   // The Areaframe takes care of all our reflow 
   // (except for when style is used to change its size?)
   nsresult rv = nsAreaFrame::Reflow(aPresContext, aDesiredSize, aReflowState, aStatus);
+  if (aDesiredSize.mComputeMEW) {
+    aDesiredSize.SetMEWToActualWidth(aReflowState.mStylePosition->mWidth.GetUnit());
+  }
   NS_FRAME_SET_TRUNCATION(aStatus, aReflowState, aDesiredSize);
   return rv;
 }
diff --git a/mozilla/layout/xul/base/src/nsBoxFrame.cpp b/mozilla/layout/xul/base/src/nsBoxFrame.cpp
index 6c39e7bbf54..64e545631a2 100644
--- a/mozilla/layout/xul/base/src/nsBoxFrame.cpp
+++ b/mozilla/layout/xul/base/src/nsBoxFrame.cpp
@@ -904,10 +904,10 @@ nsBoxFrame::Reflow(nsPresContext*          aPresContext,
   {
      nsSize minSize(0,0);
      GetMinSize(state,  minSize);
-
-     if (mRect.width > minSize.width &&
-         aReflowState.mComputedWidth == NS_INTRINSICSIZE)
-       *maxElementWidth = minSize.width;
+       if (aReflowState.mStylePosition->mWidth.GetUnit() == eStyleUnit_Percent ||
+           (mRect.width > minSize.width &&
+           aReflowState.mComputedWidth == NS_INTRINSICSIZE))
+         *maxElementWidth = minSize.width;
      else
        *maxElementWidth = mRect.width;
   }