RAL: Eliminate n^2 walk to find repaint containers

Source/core/rendering/RenderBox.cpp

Index: Source/core/rendering/RenderBox.cpp
diff --git a/Source/core/rendering/RenderBox.cpp b/Source/core/rendering/RenderBox.cpp
index 11d009accb941707f4c32527d61cc32479d105c8..e23ba02c7f40d851efbe28e2c9ca166d0a294af4 100644
--- a/Source/core/rendering/RenderBox.cpp
+++ b/Source/core/rendering/RenderBox.cpp
@@ -1546,7 +1546,7 @@ bool RenderBox::repaintLayerRectsForImage(WrappedImagePtr image, const FillLayer
     return false;
 }
 
-void RenderBox::repaintTreeAfterLayout()
+void RenderBox::repaintTreeAfterLayout(RenderLayerModelObject& repaintContainer)
 {
     // FIXME: Currently only using this logic for RenderBox and its ilk. Ideally, RenderBlockFlows with
     // inline children should track a dirty rect in local coordinates for dirty lines instead of repainting
@@ -1561,18 +1561,28 @@ void RenderBox::repaintTreeAfterLayout()
     if (!shouldCheckForInvalidationAfterLayout())
         return;
 
+    bool establishesNewRepaintContainer = isRepaintContainer();
+    RenderLayerModelObject& newRepaintContainer = *adjustCompositedContainerForSpecialAncestors(establishesNewRepaintContainer ? this : &repaintContainer);
+    // FIXME: This assert should be re-enabled when we move repaint to after compositing update. crbug.com/360286
+    // ASSERT(&newRepaintContainer == containerForRepaint());
+
     const LayoutRect oldRepaintRect = previousRepaintRect();
     const LayoutPoint oldPositionFromRepaintContainer = previousPositionFromRepaintContainer();
-    RenderLayerModelObject* repaintContainer = containerForRepaint();
-    setPreviousRepaintRect(clippedOverflowRectForRepaint(repaintContainer));
-    setPreviousPositionFromRepaintContainer(positionFromRepaintContainer(repaintContainer));
+    setPreviousRepaintRect(clippedOverflowRectForRepaint(&newRepaintContainer));
+    setPreviousPositionFromRepaintContainer(positionFromRepaintContainer(&newRepaintContainer));
 
     // If we are set to do a full repaint that means the RenderView will be
     // invalidated. We can then skip issuing of invalidations for the child
     // renderers as they'll be covered by the RenderView.
     if (view()->doingFullRepaint() && this != view()) {
-        LayoutStateMaintainer statePusher(*this, isTableRow() ? LayoutSize() : locationOffset());
-        RenderObject::repaintTreeAfterLayout();
+        // FIXME: LayoutState should be enabled for other repaint containers than the RenderView. crbug.com/363834
+        if (establishesNewRepaintContainer) {
+            LayoutStateDisabler disabler(*this);
+            RenderObject::repaintTreeAfterLayout(newRepaintContainer);
+        } else {
+            LayoutStateMaintainer statePusher(*this, isTableRow() ? LayoutSize() : locationOffset());
+            RenderObject::repaintTreeAfterLayout(newRepaintContainer);
+        }
         return;
     }
 
@@ -1585,7 +1595,7 @@ void RenderBox::repaintTreeAfterLayout()
 
     const LayoutRect& newRepaintRect = previousRepaintRect();
     const LayoutPoint& newPositionFromRepaintContainer = previousPositionFromRepaintContainer();
-    bool didFullRepaint = repaintAfterLayoutIfNeeded(containerForRepaint(),
+    bool didFullRepaint = repaintAfterLayoutIfNeeded(&newRepaintContainer,
         shouldDoFullRepaintAfterLayout(), oldRepaintRect, oldPositionFromRepaintContainer, &newRepaintRect, &newPositionFromRepaintContainer);
 
     if (!didFullRepaint)
@@ -1602,11 +1612,17 @@ void RenderBox::repaintTreeAfterLayout()
         }
     }
 
-    // FIXME: This concept of a tree walking state for fast lookups should be generalized away from
-    // just layout.
-    // FIXME: Table rows shouldn't be special-cased.
-    LayoutStateMaintainer statePusher(*this, isTableRow() ? LayoutSize() : locationOffset());
-    RenderObject::repaintTreeAfterLayout();
+    // FIXME: LayoutState should be enabled for other repaint containers than the RenderView. crbug.com/363834

[Julien - ping for review, 2014/05/07 17:50:03]

I choked on this line but Levi pointed out that we already disable LayoutState
if repaintContainer != view()

[leviw_travelin_and_unemployed, 2014/05/07 17:58:48]

As we discussed, I have a plan to fix this (which should be full of win), but am
waiting to be able to clean up the crazyness happening in LayoutState that the
old Repaint logic relies on.

+    if (establishesNewRepaintContainer) {
+        LayoutStateDisabler disabler(*this);
+        RenderObject::repaintTreeAfterLayout(newRepaintContainer);
+    } else {
+        // FIXME: This concept of a tree walking state for fast lookups should be generalized away from
+        // just layout.
+        // FIXME: Table rows shouldn't be special-cased.
+        LayoutStateMaintainer statePusher(*this, isTableRow() ? LayoutSize() : locationOffset());
+        RenderObject::repaintTreeAfterLayout(newRepaintContainer);
+    }
 }
 
 bool RenderBox::pushContentsClip(PaintInfo& paintInfo, const LayoutPoint& accumulatedOffset, ContentsClipBehavior contentsClipBehavior)