Convert main-thread overscroll parameters into viewport space.

content/renderer/render_widget.h

Index: content/renderer/render_widget.h
diff --git a/content/renderer/render_widget.h b/content/renderer/render_widget.h
index 612f2c1a53b109247b698433802057ecaa17f926..004361fd1d6a7159ca259a27bfd13e8293abc5e3 100644
--- a/content/renderer/render_widget.h
+++ b/content/renderer/render_widget.h
@@ -257,8 +257,8 @@ class CONTENT_EXPORT RenderWidget
   void resetInputMethod() override;
   void didHandleGestureEvent(const blink::WebGestureEvent& event,
                              bool event_cancelled) override;
-  void didOverscroll(const blink::WebFloatSize& unusedDelta,
-                     const blink::WebFloatSize& accumulatedRootOverScroll,
+  void didOverscroll(const blink::WebFloatSize& overscrollDelta,
+                     const blink::WebFloatSize& accumulatedOverscroll,
                      const blink::WebFloatPoint& position,
                      const blink::WebFloatSize& velocity) override;
   void showImeIfNeeded() override;