diff --git a/mozilla/layout/generic/nsLineLayout.cpp b/mozilla/layout/generic/nsLineLayout.cpp
index 343af0d520c..361ccbdeb97 100644
--- a/mozilla/layout/generic/nsLineLayout.cpp
+++ b/mozilla/layout/generic/nsLineLayout.cpp
@@ -1040,6 +1040,7 @@ nsLineLayout::ReflowFrame(nsIFrame* aFrame,
   // the float.
   if (frameType) {
     if (nsLayoutAtoms::placeholderFrame == frameType) {
+      pfd->SetFlag(PFD_ISPLACEHOLDERFRAME, PR_TRUE);
       nsIFrame* outOfFlowFrame = ((nsPlaceholderFrame*)aFrame)->GetOutOfFlowFrame();
       if (outOfFlowFrame) {
         // Make sure it's floated and not absolutely positioned
@@ -2642,9 +2643,10 @@ nsLineLayout::TrimTrailingWhiteSpaceIn(PerSpanData* psd,
         return PR_TRUE;
       }
     }
-    else if (!pfd->GetFlag(PFD_ISTEXTFRAME)) {
-      // If we hit a frame on the end that's not text, then there is
-      // no trailing whitespace to trim. Stop the search.
+    else if (!pfd->GetFlag(PFD_ISTEXTFRAME) &&
+             !pfd->GetFlag(PFD_ISPLACEHOLDERFRAME)) {
+      // If we hit a frame on the end that's not text and not a placeholder,
+      // then there is no trailing whitespace to trim. Stop the search.
       *aDeltaWidth = 0;
       return PR_TRUE;
     }
diff --git a/mozilla/layout/generic/nsLineLayout.h b/mozilla/layout/generic/nsLineLayout.h
index b4cfde44b84..7e5e5c4aa43 100644
--- a/mozilla/layout/generic/nsLineLayout.h
+++ b/mozilla/layout/generic/nsLineLayout.h
@@ -353,7 +353,8 @@ protected:
 #define PFD_ISLETTERFRAME               0x00000010
 #define PFD_ISSTICKY                    0x00000020
 #define PFD_ISBULLET                    0x00000040
-#define PFD_LASTFLAG                    PFD_ISBULLET
+#define PFD_ISPLACEHOLDERFRAME          0x00000080
+#define PFD_LASTFLAG                    PFD_ISPLACEHOLDERFRAME
 
     PRPackedBool mFlags;
 
diff --git a/mozilla/layout/html/base/src/nsLineLayout.cpp b/mozilla/layout/html/base/src/nsLineLayout.cpp
index 343af0d520c..361ccbdeb97 100644
--- a/mozilla/layout/html/base/src/nsLineLayout.cpp
+++ b/mozilla/layout/html/base/src/nsLineLayout.cpp
@@ -1040,6 +1040,7 @@ nsLineLayout::ReflowFrame(nsIFrame* aFrame,
   // the float.
   if (frameType) {
     if (nsLayoutAtoms::placeholderFrame == frameType) {
+      pfd->SetFlag(PFD_ISPLACEHOLDERFRAME, PR_TRUE);
       nsIFrame* outOfFlowFrame = ((nsPlaceholderFrame*)aFrame)->GetOutOfFlowFrame();
       if (outOfFlowFrame) {
         // Make sure it's floated and not absolutely positioned
@@ -2642,9 +2643,10 @@ nsLineLayout::TrimTrailingWhiteSpaceIn(PerSpanData* psd,
         return PR_TRUE;
       }
     }
-    else if (!pfd->GetFlag(PFD_ISTEXTFRAME)) {
-      // If we hit a frame on the end that's not text, then there is
-      // no trailing whitespace to trim. Stop the search.
+    else if (!pfd->GetFlag(PFD_ISTEXTFRAME) &&
+             !pfd->GetFlag(PFD_ISPLACEHOLDERFRAME)) {
+      // If we hit a frame on the end that's not text and not a placeholder,
+      // then there is no trailing whitespace to trim. Stop the search.
       *aDeltaWidth = 0;
       return PR_TRUE;
     }
diff --git a/mozilla/layout/html/base/src/nsLineLayout.h b/mozilla/layout/html/base/src/nsLineLayout.h
index b4cfde44b84..7e5e5c4aa43 100644
--- a/mozilla/layout/html/base/src/nsLineLayout.h
+++ b/mozilla/layout/html/base/src/nsLineLayout.h
@@ -353,7 +353,8 @@ protected:
 #define PFD_ISLETTERFRAME               0x00000010
 #define PFD_ISSTICKY                    0x00000020
 #define PFD_ISBULLET                    0x00000040
-#define PFD_LASTFLAG                    PFD_ISBULLET
+#define PFD_ISPLACEHOLDERFRAME          0x00000080
+#define PFD_LASTFLAG                    PFD_ISPLACEHOLDERFRAME
 
     PRPackedBool mFlags;