Move LayoutObject::m_previousPosition... into a global map in ObjectPaintInvalidator

third_party/WebKit/Source/core/layout/LayoutObject.cpp

Index: third_party/WebKit/Source/core/layout/LayoutObject.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutObject.cpp b/third_party/WebKit/Source/core/layout/LayoutObject.cpp
index 4bc424f28d5ab16209b5cc6bb02ce91bff555f63..0cbc8e0503344324cdad1f27fa09fd077405be2a 100644
--- a/third_party/WebKit/Source/core/layout/LayoutObject.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutObject.cpp
@@ -127,7 +127,6 @@ struct SameSizeAsLayoutObject : DisplayItemClient {
   unsigned m_bitfields;
   unsigned m_bitfields2;
   LayoutRect m_previousVisualRect;
-  LayoutPoint m_previousPosition;
 };
 
 static_assert(sizeof(LayoutObject) == sizeof(SameSizeAsLayoutObject),
@@ -1204,11 +1203,15 @@ PaintInvalidationReason LayoutObject::invalidatePaintIfNeeded(
       paintInvalidationState.paintInvalidationContainer();
   DCHECK(paintInvalidationContainer == containerForPaintInvalidation());
 
+  ObjectPaintInvalidator paintInvalidator(*this);
   context.oldVisualRect = previousVisualRect();
-  context.oldLocation = previousPositionFromPaintInvalidationBacking();
+  context.oldLocation = paintInvalidator.previousLocationInBacking();
   context.newVisualRect = paintInvalidationState.computeVisualRectInBacking();
-  context.newLocation =
-      paintInvalidationState.computePositionFromPaintInvalidationBacking();
+  // Use visual rect location for LayoutTexts and non-container SVG objects
+  // because visual rect change suffices to detect layout caused invalidation.
+  context.newLocation = !isBoxModelObject() && !isSVGContainer()

[chrishtr, 2016/11/04 18:20:06]

You don't need a conditional here I think.
paintInvalidationState.computeLocationInBacking already does
the conditional for you.

[Xianzhu, 2016/11/04 19:11:03]

They are in different paths (PaintInvalidator path vs PaintInvalidationState
path). Now put the check into
PaintInvalidationState::computePreviousLocationInBacking().

+                            ? context.newVisualRect.location()
+                            : paintInvalidationState.computeLocationInBacking();
 
   IntSize adjustment =
       scrollAdjustmentForPaintInvalidation(paintInvalidationContainer);
@@ -1218,7 +1221,7 @@ PaintInvalidationReason LayoutObject::invalidatePaintIfNeeded(
   adjustVisualRectForRasterEffects(context.newVisualRect);
 
   setPreviousVisualRect(context.newVisualRect);
-  setPreviousPositionFromPaintInvalidationBacking(context.newLocation);
+  paintInvalidator.setPreviousLocationInBacking(context.newLocation);
 
   if (!shouldCheckForPaintInvalidationRegardlessOfPaintInvalidationState() &&
       paintInvalidationState