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 72705a74854f0b8a1758496e4ffd8843d923b3b9..67b6198dd78b7e1c3a754718ac7ba3d0c891c2ba 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);
@@ -1507,6 +1507,19 @@ void RenderViewImpl::SendUpdateState(HistoryEntry* entry) {
       routing_id_, page_id_, HistoryEntryToPageState(entry)));
 }
 
+void RenderViewImpl::ApplyWebPreferencesInternal(
+    const WebPreferences& prefs,
+    blink::WebView* web_view,
+    CompositorDependencies* compositor_deps) {
+  ApplyWebPreferences(prefs, web_view);
+#if defined(OS_MACOSX) && !defined(OS_IOS)
+  DCHECK(compositor_deps);
+  bool is_elastic_overscroll_enabled =
+      compositor_deps->IsElasticOverscrollEnabled();
+  web_view->settings()->setReportWheelOverscroll(is_elastic_overscroll_enabled);
+#endif
+}
+
 bool RenderViewImpl::SendAndRunNestedMessageLoop(IPC::SyncMessage* message) {
   // Before WebKit asks us to show an alert (etc.), it takes care of doing the
   // equivalent of WebView::willEnterModalLoop.  In the case of showModalDialog
@@ -2650,7 +2663,7 @@ void RenderViewImpl::OnDragSourceSystemDragEnded() {
 
 void RenderViewImpl::OnUpdateWebPreferences(const WebPreferences& prefs) {
   webkit_preferences_ = prefs;
-  ApplyWebPreferences(webkit_preferences_, webview());
+  ApplyWebPreferencesInternal(webkit_preferences_, webview(), compositor_deps_);
 }
 
 void RenderViewImpl::OnEnumerateDirectoryResponse(