Move paint offset paint invalidation into PaintPropertyTreeBuilder

Paint offset changes should cause full paint invalidation in SPV2,
but this tracking logic can be squirreled away in
PaintPropertyTreeBuilder. This removes SPV2-specific paint offset
code from PrePaintTreeWalk::walk which was visibile on profiles
of the blink_perf.paint paint-offset-changes test.

This approach also lets us use the paint offset under-invalidation
checking in FindPropertiesNeedingUpdate which would miss changes
to a LayoutObject's paint offset outside the under-invalidation
checking scopes in PaintPropertyTreeBuilder.

BUG=678597
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2

Review-Url: https://codereview.chromium.org/2644453002
Cr-Commit-Position: refs/heads/master@{#444411}

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

@@ -378,17 +378,13 @@ void PaintInvalidator::invalidatePaintIfNeeded(
 
 void PaintInvalidator::invalidatePaintIfNeeded(
     const LayoutObject& object,
-    const LayoutPoint& oldPaintOffset,
     PaintInvalidatorContext& context) {
   object.getMutableForPainting().ensureIsReadyForPaintInvalidation();
 
+  // The paint offset should already be updated through
+  // PaintPropertyTreeBuilder::updatePropertiesForSelf.
   DCHECK(context.treeBuilderContext.current.paintOffset ==
          object.paintOffset());
-  if (RuntimeEnabledFeatures::slimmingPaintV2Enabled() &&
-      object.paintOffset() != oldPaintOffset) {
-    object.getMutableForPainting().setShouldDoFullPaintInvalidation(
-        PaintInvalidationLocationChange);
-  }
 
   if (!context.forcedSubtreeInvalidationFlags &&
       !object

third_party/WebKit/Source/core/paint/PaintInvalidator.h

@@ -87,9 +87,7 @@ struct PaintInvalidatorContext {
 class PaintInvalidator {
  public:
   void invalidatePaintIfNeeded(FrameView&, PaintInvalidatorContext&);
-  void invalidatePaintIfNeeded(const LayoutObject&,
-                               const LayoutPoint& oldPaintOffset,
-                               PaintInvalidatorContext&);
+  void invalidatePaintIfNeeded(const LayoutObject&, PaintInvalidatorContext&);
 
   // Process objects needing paint invalidation on the next frame.
   // See the definition of PaintInvalidationDelayedFull for more details.

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

@@ -968,8 +968,14 @@ void PaintPropertyTreeBuilder::updatePropertiesForSelf(
     updateScrollbarPaintOffset(object, context);
   }
 
-  if (object.needsPaintPropertyUpdate() || context.forceSubtreeUpdate)
+  if (object.needsPaintPropertyUpdate() || context.forceSubtreeUpdate) {
+    if (RuntimeEnabledFeatures::slimmingPaintV2Enabled() &&
+        object.paintOffset() != context.current.paintOffset) {
+      object.getMutableForPainting().setShouldDoFullPaintInvalidation(
+          PaintInvalidationLocationChange);
+    }
     object.getMutableForPainting().setPaintOffset(context.current.paintOffset);
+  }
 }
 
 void PaintPropertyTreeBuilder::updatePropertiesForChildren(

third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.h

@@ -106,7 +106,8 @@ class PaintPropertyTreeBuilder {
                                    PaintPropertyTreeBuilderContext&);
 
   // Update the paint properties that affect this object (e.g., properties like
-  // paint offset translation) and ensure the context is up to date.
+  // paint offset translation) and ensure the context is up to date. Also
+  // handles updating the object's paintOffset.
   void updatePropertiesForSelf(const LayoutObject&,
                                PaintPropertyTreeBuilderContext&);
   // Update the paint properties that affect children of this object (e.g.,

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

@@ -103,7 +103,6 @@ bool PrePaintTreeWalk::walk(const LayoutObject& object,
   // Ensure the current context takes into account the box's position. This can
   // force a subtree update due to paint offset changes and must precede any
   // early out from the treewalk.
-  LayoutPoint oldPaintOffset = object.paintOffset();
   m_propertyTreeBuilder.updateContextForBoxPosition(object,
                                                     context.treeBuilderContext);
 
@@ -121,7 +120,7 @@ bool PrePaintTreeWalk::walk(const LayoutObject& object,
 
   m_propertyTreeBuilder.updatePropertiesForSelf(object,
                                                 context.treeBuilderContext);
-  m_paintInvalidator.invalidatePaintIfNeeded(object, oldPaintOffset,
+  m_paintInvalidator.invalidatePaintIfNeeded(object,
                                              context.paintInvalidatorContext);
   m_propertyTreeBuilder.updatePropertiesForChildren(object,
                                                     context.treeBuilderContext);