Fix descendant-dependent PaintLayer flags update to not early-out when dirty.

third_party/WebKit/Source/core/paint/PaintLayer.cpp

Index: third_party/WebKit/Source/core/paint/PaintLayer.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintLayer.cpp b/third_party/WebKit/Source/core/paint/PaintLayer.cpp
index 535f90699c94aab02253d897aec7dfe7afe65e9b..2f554d52ec489634ce3b879c027b93f750497e25 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayer.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintLayer.cpp
@@ -640,7 +640,6 @@ void PaintLayer::mapRectToPaintInvalidationBacking(
 }
 
 void PaintLayer::dirtyVisibleContentStatus() {
-  compositor()->setNeedsUpdateDescendantDependentFlags();
   m_isVisibleContentDirty = true;
   if (parent())
     parent()->dirtyAncestorChainVisibleDescendantStatus();
@@ -659,8 +658,6 @@ void PaintLayer::potentiallyDirtyVisibleContentStatus(EVisibility visibility) {
 }
 
 void PaintLayer::dirtyAncestorChainVisibleDescendantStatus() {
-  compositor()->setNeedsUpdateDescendantDependentFlags();
-
   for (PaintLayer* layer = this; layer; layer = layer->parent()) {
     if (layer->m_isVisibleDescendantDirty)
       break;
@@ -704,10 +701,8 @@ void PaintLayer::updateDescendantDependentFlags() {
          child = child->nextSibling()) {
       child->updateDescendantDependentFlags();
 
-      if (child->m_hasVisibleContent || child->m_hasVisibleDescendant) {
+      if (child->m_hasVisibleContent || child->m_hasVisibleDescendant)
         m_hasVisibleDescendant = true;
-        break;

[chrishtr, 2016/11/30 15:26:38]

Here is where it used to incorrectly early-out of the iteration over children.
There are about
10 layout tests that fail if the "whole subtree" hammer is removed but this
break remains.

-      }
     }
 
     m_isVisibleDescendantDirty = false;