mozilla-central: changeset 487937:127c7dfc011a16a64076b300ccb151634cec704f

author	Mats Palmgren <mats@mozilla.com>
	Wed, 14 Aug 2019 14:33:46 +0000
changeset 487937	127c7dfc011a16a64076b300ccb151634cec704f
parent 487936	6bb15997aba70ca39a931eb9dc83cfd7d84ed683
child 487938	62b047361030e2f2e963f1e5621daea812720bff
push id	36433
push user	btara@mozilla.com
push date	Wed, 14 Aug 2019 21:57:52 +0000
treeherder	mozilla-central@7d9a2196d313 [default view] [failures only]
perfherder	[talos] [build metrics] [platform microbench] (compared to previous push)
reviewers	emilio
bugs	1038294
milestone	70.0a1
first release with	nightly linux32 7d9a2196d313 / 70.0a1 / 20190814215752 / files nightly linux64 7d9a2196d313 / 70.0a1 / 20190814215752 / files nightly mac 7d9a2196d313 / 70.0a1 / 20190814215752 / files nightly win32 7d9a2196d313 / 70.0a1 / 20190814215752 / files nightly win64 7d9a2196d313 / 70.0a1 / 20190814215752 / files
last release without	nightly linux32 58400ee2747a / 70.0a1 / 20190813095543 / files nightly linux64 58400ee2747a / 70.0a1 / 20190813095543 / files nightly mac 58400ee2747a / 70.0a1 / 20190813095543 / files nightly win32 58400ee2747a / 70.0a1 / 20190813095543 / files nightly win64 58400ee2747a / 70.0a1 / 20190813095543 / files

--- a/layout/base/nsCSSFrameConstructor.cpp
+++ b/layout/base/nsCSSFrameConstructor.cpp
@@ -4359,39 +4359,19 @@ nsCSSFrameConstructor::FindDisplayData(c
   // and that might need to be propagated.
   // XXXbz is this the right place to do this?  If this code moves,
   // make this function static.
   bool propagatedScrollToViewport = false;
   if (aElement.IsHTMLElement(nsGkAtoms::body)) {
     if (nsPresContext* presContext = mPresShell->GetPresContext()) {
       propagatedScrollToViewport =
           presContext->UpdateViewportScrollStylesOverride() == &aElement;
-    }
-  }
-
-  NS_ASSERTION(!propagatedScrollToViewport ||
-                   !mPresShell->GetPresContext()->IsPaginated(),
-               "Shouldn't propagate scroll in paginated contexts");
-
-  // If this is for a <body> node and we've propagated the scroll-frame to the
-  // viewport, we need to make sure not to add another layer of scrollbars, so
-  // we use a different FCData struct without FCDATA_MAY_NEED_SCROLLFRAME.
-  if (propagatedScrollToViewport && aDisplay.IsScrollableOverflow()) {
-    if (aDisplay.mDisplay == StyleDisplay::Flex ||
-        aDisplay.mDisplay == StyleDisplay::WebkitBox ||
-        (StaticPrefs::layout_css_emulate_moz_box_with_flex() &&
-         aDisplay.mDisplay == StyleDisplay::MozBox)) {
-      static const FrameConstructionData sNonScrollableFlexData =
-          FCDATA_DECL(0, NS_NewFlexContainerFrame);
-      return &sNonScrollableFlexData;
-    }
-    if (aDisplay.mDisplay == StyleDisplay::Grid) {
-      static const FrameConstructionData sNonScrollableGridData =
-          FCDATA_DECL(0, NS_NewGridContainerFrame);
-      return &sNonScrollableGridData;
+      MOZ_ASSERT(!propagatedScrollToViewport ||
+                     !mPresShell->GetPresContext()->IsPaginated(),
+                 "Shouldn't propagate scroll in paginated contexts");
     }
   }
 
   switch (aDisplay.mDisplay) {
 #ifdef DEBUG
     case StyleDisplay::None:
     case StyleDisplay::Contents:
       MOZ_ASSERT_UNREACHABLE("should have been handled earlier");
@@ -4537,25 +4517,29 @@ nsCSSFrameConstructor::FindDisplayData(c
         return &data;
       }
       MOZ_FALLTHROUGH;
     }
     case StyleDisplay::Flex:
     case StyleDisplay::InlineFlex:
     case StyleDisplay::WebkitBox:
     case StyleDisplay::WebkitInlineBox: {
+      static const FrameConstructionData nonScrollableData =
+        FCDATA_DECL(0, NS_NewFlexContainerFrame);
       static const FrameConstructionData data =
         FCDATA_DECL(FCDATA_MAY_NEED_SCROLLFRAME, NS_NewFlexContainerFrame);
-      return &data;
+      return MOZ_UNLIKELY(propagatedScrollToViewport) ? &nonScrollableData : &data;
     }
     case StyleDisplay::Grid:
     case StyleDisplay::InlineGrid: {
+      static const FrameConstructionData nonScrollableData =
+        FCDATA_DECL(0, NS_NewGridContainerFrame);
       static const FrameConstructionData data =
         FCDATA_DECL(FCDATA_MAY_NEED_SCROLLFRAME, NS_NewGridContainerFrame);
-      return &data;
+      return MOZ_UNLIKELY(propagatedScrollToViewport) ? &nonScrollableData : &data;
     }
     case StyleDisplay::Ruby: {
       static const FrameConstructionData data =
         FCDATA_DECL(FCDATA_IS_LINE_PARTICIPANT, NS_NewRubyFrame);
       return &data;
     }
     case StyleDisplay::RubyBase: {
       static const FrameConstructionData data =