Setting Accurate ScrollResult from Blink for Elastic Scroll.

content/renderer/render_view_impl.cc

Index: content/renderer/render_view_impl.cc
diff --git a/content/renderer/render_view_impl.cc b/content/renderer/render_view_impl.cc
index bb881cbbd0bdf2581d61e758bd9e8c9974b8a082..ff531257ea392e0767fe96e7b5a0e912417013c7 100644
--- a/content/renderer/render_view_impl.cc
+++ b/content/renderer/render_view_impl.cc
@@ -762,7 +762,7 @@ void RenderViewImpl::Initialize(const ViewMsg_New_Params& params,
   webview()->settings()->setRootLayerScrolls(
       command_line.HasSwitch(switches::kRootLayerScrolls));
 
-  ApplyWebPreferences(webkit_preferences_, webview());
+  ApplyWebPreferencesInternal(webkit_preferences_, webview(), compositor_deps_);
 
   if (switches::IsTouchDragDropEnabled())
     webview()->settings()->setTouchDragDropEnabled(true);
@@ -907,8 +907,10 @@ void RenderView::ForEach(RenderViewVisitor* visitor) {
 }
 
 /*static*/
-void RenderView::ApplyWebPreferences(const WebPreferences& prefs,
-                                     WebView* web_view) {
+void RenderView::ApplyWebPreferencesInternal(
+    const WebPreferences& prefs,
+    WebView* web_view,
+    CompositorDependencies* compositor_deps) {
   WebSettings* settings = web_view->settings();
   ApplyFontsFromMap(prefs.standard_font_family_map,
                     SetStandardFontFamilyWrapper, settings);
@@ -1134,6 +1136,11 @@ void RenderView::ApplyWebPreferences(const WebPreferences& prefs,
   settings->setShowContextMenuOnMouseUp(prefs.context_menu_on_mouse_up);
 
 #if defined(OS_MACOSX)
+#if !defined(OS_IOS)
+  bool is_elastic_overscroll_enabled =
+      compositor_deps ? compositor_deps->IsElasticOverscrollEnabled() : false;
+  settings->setReportWheelOverscroll(is_elastic_overscroll_enabled);
+#endif
   settings->setDoubleTapToZoomEnabled(true);
   web_view->setMaximumLegibleScale(prefs.default_maximum_page_scale_factor);
 #endif
@@ -2646,7 +2653,7 @@ void RenderViewImpl::OnDragSourceSystemDragEnded() {
 
 void RenderViewImpl::OnUpdateWebPreferences(const WebPreferences& prefs) {
   webkit_preferences_ = prefs;
-  ApplyWebPreferences(webkit_preferences_, webview());
+  ApplyWebPreferencesInternal(webkit_preferences_, webview(), NULL);
 }
 
 void RenderViewImpl::OnEnumerateDirectoryResponse(