[SPInvalidation] Handle pixel-snapping of paint invalidation rects

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

Index: third_party/WebKit/Source/core/layout/LayoutObject.h
diff --git a/third_party/WebKit/Source/core/layout/LayoutObject.h b/third_party/WebKit/Source/core/layout/LayoutObject.h
index 55bc604d5846fbe7b08cabc01c8ebf4041a077f9..d22f6d42bd75b3e8de00b81773ea4e77be0607c4 100644
--- a/third_party/WebKit/Source/core/layout/LayoutObject.h
+++ b/third_party/WebKit/Source/core/layout/LayoutObject.h
@@ -1598,6 +1598,12 @@ class CORE_EXPORT LayoutObject : public ImageResourceObserver,
     return m_previousPaintInvalidationRect;
   }
 
+  // The previous paint invalidation rect may have been expanded to whole pixels
+  // or be rotated, skewed, etc., so covers more pixels than the object covers.
+  bool previousPaintInvalidationRectCoversExtraPixels() const {

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

I wonder if "*ExpandedForSnapping" would be more descriptive than
"*CoversExtraPixels"?

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

In next steps, the field will be also used for transforms with rotate, skew etc.
which also causes the rect to cover extra pixels. See TODO(crbug.com/426111) in
BoxPaintInvalidator.cpp.

+    return m_bitfields.previousPaintInvalidationRectCoversExtraPixels();
+  }
+
   // Called when the previous paint invalidation rect(s) is no longer valid.
   virtual void clearPreviousPaintInvalidationRects();
 
@@ -1704,8 +1710,11 @@ class CORE_EXPORT LayoutObject : public ImageResourceObserver,
       m_layoutObject.ensureIsReadyForPaintInvalidation();
     }
 
-    void setPreviousPaintInvalidationRect(const LayoutRect& r) {
+    void setPreviousPaintInvalidationRect(const LayoutRect& r,
+                                          bool coversExtraPixels) {
       m_layoutObject.setPreviousPaintInvalidationRect(r);
+      m_layoutObject.m_bitfields
+          .setPreviousPaintInvalidationRectCoversExtraPixels(coversExtraPixels);
     }
     void setPreviousPositionFromPaintInvalidationBacking(const LayoutPoint& p) {
       m_layoutObject.setPreviousPositionFromPaintInvalidationBacking(p);
@@ -2092,6 +2101,7 @@ class CORE_EXPORT LayoutObject : public ImageResourceObserver,
           m_mayNeedPaintInvalidationSubtree(false),
           m_mayNeedPaintInvalidationAnimatedBackgroundImage(false),
           m_shouldInvalidateSelection(false),
+          m_previousPaintInvalidationRectCoversExtraPixels(false),
           m_floating(false),
           m_isAnonymous(!node),
           m_isText(false),
@@ -2123,7 +2133,7 @@ class CORE_EXPORT LayoutObject : public ImageResourceObserver,
           m_backgroundObscurationState(BackgroundObscurationStatusInvalid),
           m_fullPaintInvalidationReason(PaintInvalidationNone) {}
 
-    // 32 bits have been used in the first word, and 19 in the second.
+    // 32 bits have been used in the first word, and 20 in the second.
 
     // Self needs layout means that this layout object is marked for a full
     // layout. This is the default layout but it is expensive as it recomputes
@@ -2191,6 +2201,9 @@ class CORE_EXPORT LayoutObject : public ImageResourceObserver,
                          MayNeedPaintInvalidationAnimatedBackgroundImage);
     ADD_BOOLEAN_BITFIELD(shouldInvalidateSelection, ShouldInvalidateSelection);
 
+    ADD_BOOLEAN_BITFIELD(previousPaintInvalidationRectCoversExtraPixels,
+                         PreviousPaintInvalidationRectCoversExtraPixels);
+
     // This boolean is the cached value of 'float'
     // (see ComputedStyle::isFloating).
     ADD_BOOLEAN_BITFIELD(floating, Floating);