Fix gradient background invalidation when HTML size changes

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

Index: third_party/WebKit/Source/core/paint/BoxPaintInvalidator.h
diff --git a/third_party/WebKit/Source/core/paint/BoxPaintInvalidator.h b/third_party/WebKit/Source/core/paint/BoxPaintInvalidator.h
index 76e2b8ec581220d71f25ebff98182fce2d4e14f8..7d7c811681390f6ce7e82a3dfc7fafb299e531f6 100644
--- a/third_party/WebKit/Source/core/paint/BoxPaintInvalidator.h
+++ b/third_party/WebKit/Source/core/paint/BoxPaintInvalidator.h
@@ -27,6 +27,9 @@ class BoxPaintInvalidator {
 
   PaintInvalidationReason invalidatePaintIfNeeded();
 
+  static LayoutSize previousBorderBoxSize(const LayoutBox&,
+                                          const LayoutSize& defaultSize);
+
  private:
   bool backgroundGeometryDependsOnLayoutOverflowRect();
   bool backgroundPaintsOntoScrollingContentsLayer();
@@ -43,7 +46,6 @@ class BoxPaintInvalidator {
 
   bool needsToSavePreviousBoxGeometries();
   void savePreviousBoxGeometriesIfNeeded();
-  LayoutSize previousBorderBoxSize();
   LayoutRect previousContentBoxRect();
   LayoutRect previousLayoutOverflowRect();