Implement incremental paint property tree rebuilding

third_party/WebKit/Source/core/frame/FrameView.h

Index: third_party/WebKit/Source/core/frame/FrameView.h
diff --git a/third_party/WebKit/Source/core/frame/FrameView.h b/third_party/WebKit/Source/core/frame/FrameView.h
index 4419f0c5a9bc85c9c156bda820d95ee6ba10c10f..7afacec88119ed27cceb6ea984fc2837e3cb65dd 100644
--- a/third_party/WebKit/Source/core/frame/FrameView.h
+++ b/third_party/WebKit/Source/core/frame/FrameView.h
@@ -718,6 +718,18 @@ class CORE_EXPORT FrameView final
     return m_totalPropertyTreeStateForContents.get();
   }
 
+  // Paint properties (e.g., m_preTranslation, etc.) are built from the
+  // FrameView's state (e.g., x(), y(), etc.) and need to be invalidated when
+  // these values change (see: PaintPropertyTreeBuilder::updateProperties).
+  // Invalid paint properties will be rebuilt during the next lifecycle update
+  // (see: FrameView::updatePaintProperties).
+  void setPaintPropertiesInvalid() { m_paintPropertiesValid = false; }

[chrishtr, 2016/10/21 22:03:09]

...Invalid is different nomenclature from invalidations on other tree walks for
layout, paint invalidation, etc.
What common naming scheme should we use?

[pdr., 2016/10/26 03:10:48]

I've switched this to the following which is similar to layout and paint
invalidation:
setNeedsPropertyUpdate()
clearNeedsPropertyUpdate()

I've also added comments about how we can expand this in the future. Possibly
something along these lines:
setNeedsLocalPropertyUpdate()
setNeedsSubtreePropertyUpdate()
...etc

+  void setPaintPropertiesValid() {
+    DCHECK_EQ(lifecycle().state(), DocumentLifecycle::InPrePaint);
+    m_paintPropertiesValid = true;
+  }
+  bool paintPropertiesValid() const { return m_paintPropertiesValid; }
+
   // TODO(ojan): Merge this with IntersectionObserver once it lands.
   IntRect computeVisibleArea();
 
@@ -1059,6 +1071,9 @@ class CORE_EXPORT FrameView final
   // properties are either created by this FrameView or are inherited from
   // an ancestor.
   std::unique_ptr<PropertyTreeState> m_totalPropertyTreeStateForContents;
+  // True if the paint properties are up-to-date with the FrameView's state.
+  // See: setPaintPropertiesValid and setPaintPropertiesInvalid.
+  bool m_paintPropertiesValid = false;
 
   // This is set on the local root frame view only.
   DocumentLifecycle::LifecycleState m_currentUpdateLifecyclePhasesTargetState;