[SPInvalidation] Handle pixel-snapping of paint invalidation rects

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

Index: third_party/WebKit/Source/core/paint/PaintInvalidator.h
diff --git a/third_party/WebKit/Source/core/paint/PaintInvalidator.h b/third_party/WebKit/Source/core/paint/PaintInvalidator.h
index 68c7e5aa0312ec396be16cb188cd2ba363912e4a..6b62c6548a70959098a82f90d8212a666bf4ce87 100644
--- a/third_party/WebKit/Source/core/paint/PaintInvalidator.h
+++ b/third_party/WebKit/Source/core/paint/PaintInvalidator.h
@@ -72,6 +72,8 @@ struct PaintInvalidatorContext {
   LayoutRect newBounds;
   LayoutPoint oldLocation;
   LayoutPoint newLocation;
+  bool oldBoundsCoversExtraPixels = false;
+  bool newBoundsCoversExtraPixels = false;
 };
 
 class PaintInvalidator {
@@ -87,10 +89,12 @@ class PaintInvalidator {
   LayoutRect mapLocalRectToPaintInvalidationBacking(
       const LayoutObject&,
       const FloatRect&,
-      const PaintInvalidatorContext&);
+      const PaintInvalidatorContext&,
+      bool& coversExtraPixels);
   LayoutRect computePaintInvalidationRectInBacking(

[pdr., 2016/10/26 05:25:12]

Returning through both a return value and an out-param is a little confusing.
WDYT of making them both out-params, or returning something like:
struct PaintInvalidationRectInBacking {
    LayoutRect rect;
    bool coversExtraPixels;
}

[Xianzhu, 2016/10/26 18:32:31]

Done.

       const LayoutObject&,
-      const PaintInvalidatorContext&);
+      const PaintInvalidatorContext&,
+      bool& coversExtraPixels);
   LayoutPoint computeLocationFromPaintInvalidationBacking(
       const LayoutObject&,
       const PaintInvalidatorContext&);