diff --git a/mozilla/layout/base/nsCSSFrameConstructor.cpp b/mozilla/layout/base/nsCSSFrameConstructor.cpp
index 0e28c10eb78..a07e3d09189 100644
--- a/mozilla/layout/base/nsCSSFrameConstructor.cpp
+++ b/mozilla/layout/base/nsCSSFrameConstructor.cpp
@@ -4316,10 +4316,8 @@ nsCSSFrameConstructor::InitializeSelectFrame(nsIPresShell*        aPresShell,
   // Process children
   nsFrameConstructorSaveState absoluteSaveState;
   nsFrameItems                childItems;
-  const nsStyleDisplay*       display = aStyleContext->GetStyleDisplay();
-  PRBool isPositionedContainingBlock = aIsAbsolutelyPositioned ||
-                                       aIsFixedPositioned ||
-                                       display->mPosition == NS_STYLE_POSITION_RELATIVE;
+  PRBool                      isPositionedContainingBlock = aIsAbsolutelyPositioned ||
+    aIsFixedPositioned;
 
   if (isPositionedContainingBlock) {
     // The area frame becomes a container for child frames that are
@@ -4425,10 +4423,8 @@ nsCSSFrameConstructor::ConstructFieldSetFrame(nsIPresShell*            aPresShel
   // Process children
   nsFrameConstructorSaveState absoluteSaveState;
   nsFrameItems                childItems;
-  const nsStyleDisplay*       display = aStyleContext->GetStyleDisplay();
-  PRBool isPositionedContainingBlock = aIsAbsolutelyPositioned ||
-                                       aIsFixedPositioned ||
-                                       display->mPosition == NS_STYLE_POSITION_RELATIVE;
+  PRBool                      isPositionedContainingBlock = aIsAbsolutelyPositioned ||
+    aIsFixedPositioned;
 
   if (isPositionedContainingBlock) {
     // The area frame becomes a container for child frames that are
@@ -6201,9 +6197,8 @@ nsCSSFrameConstructor::ConstructFrameByDisplayType(nsIPresShell*            aPre
     // Process children
     nsFrameConstructorSaveState absoluteSaveState;
     nsFrameItems                childItems;
-    PRBool isPositionedContainingBlock = isAbsolutelyPositioned ||
-                                         isFixedPositioned ||
-                                         aDisplay->mPosition == NS_STYLE_POSITION_RELATIVE;
+    PRBool                      isPositionedContainingBlock = isAbsolutelyPositioned ||
+                                                              isFixedPositioned;
 
     if (isPositionedContainingBlock) {
       // The area frame becomes a container for child frames that are
diff --git a/mozilla/layout/html/style/src/nsCSSFrameConstructor.cpp b/mozilla/layout/html/style/src/nsCSSFrameConstructor.cpp
index 0e28c10eb78..a07e3d09189 100644
--- a/mozilla/layout/html/style/src/nsCSSFrameConstructor.cpp
+++ b/mozilla/layout/html/style/src/nsCSSFrameConstructor.cpp
@@ -4316,10 +4316,8 @@ nsCSSFrameConstructor::InitializeSelectFrame(nsIPresShell*        aPresShell,
   // Process children
   nsFrameConstructorSaveState absoluteSaveState;
   nsFrameItems                childItems;
-  const nsStyleDisplay*       display = aStyleContext->GetStyleDisplay();
-  PRBool isPositionedContainingBlock = aIsAbsolutelyPositioned ||
-                                       aIsFixedPositioned ||
-                                       display->mPosition == NS_STYLE_POSITION_RELATIVE;
+  PRBool                      isPositionedContainingBlock = aIsAbsolutelyPositioned ||
+    aIsFixedPositioned;
 
   if (isPositionedContainingBlock) {
     // The area frame becomes a container for child frames that are
@@ -4425,10 +4423,8 @@ nsCSSFrameConstructor::ConstructFieldSetFrame(nsIPresShell*            aPresShel
   // Process children
   nsFrameConstructorSaveState absoluteSaveState;
   nsFrameItems                childItems;
-  const nsStyleDisplay*       display = aStyleContext->GetStyleDisplay();
-  PRBool isPositionedContainingBlock = aIsAbsolutelyPositioned ||
-                                       aIsFixedPositioned ||
-                                       display->mPosition == NS_STYLE_POSITION_RELATIVE;
+  PRBool                      isPositionedContainingBlock = aIsAbsolutelyPositioned ||
+    aIsFixedPositioned;
 
   if (isPositionedContainingBlock) {
     // The area frame becomes a container for child frames that are
@@ -6201,9 +6197,8 @@ nsCSSFrameConstructor::ConstructFrameByDisplayType(nsIPresShell*            aPre
     // Process children
     nsFrameConstructorSaveState absoluteSaveState;
     nsFrameItems                childItems;
-    PRBool isPositionedContainingBlock = isAbsolutelyPositioned ||
-                                         isFixedPositioned ||
-                                         aDisplay->mPosition == NS_STYLE_POSITION_RELATIVE;
+    PRBool                      isPositionedContainingBlock = isAbsolutelyPositioned ||
+                                                              isFixedPositioned;
 
     if (isPositionedContainingBlock) {
       // The area frame becomes a container for child frames that are