Add convenience methods for PLSA visible client dimensions.

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

Index: third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.h
diff --git a/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.h b/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.h
index a00b42bb565f10b645cde6b8b1ffc33bbdfc8a6b..c9683ae60dde99f05576f779e594b990bad25c79 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.h
+++ b/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.h
@@ -297,6 +297,16 @@ class CORE_EXPORT PaintLayerScrollableArea final
   CompositorAnimationHost* GetCompositorAnimationHost() const override;
   CompositorAnimationTimeline* GetCompositorAnimationTimeline() const override;
 
+  // These are temporary convenience methods.  They delegate to Box() methods,
+  // which will be up-to-date when UpdateAfterLayout runs.  By contrast,
+  // VisibleContentRect() is based on layer_.Size(), which isn't updated
+  // until later, when UpdateLayerPosition runs.  A future patch will cause
+  // layer_.Size() to be updated effectively simultaneously with Box()
+  // sizing.  When that lands, these methods should be removed in favor of
+  // using VisibleContentRect() and/or layer_.Size() everywhere.
+  LayoutSize ClientSize() const;
+  IntSize PixelSnappedClientSize() const;
+
   void VisibleSizeChanged();
 
   // FIXME: We shouldn't allow access to m_overflowRect outside this class.