Bubble scroll events from WebView guest to embedder.

content/renderer/browser_plugin/browser_plugin.cc

Index: content/renderer/browser_plugin/browser_plugin.cc
diff --git a/content/renderer/browser_plugin/browser_plugin.cc b/content/renderer/browser_plugin/browser_plugin.cc
index c2b73247e2508f3ab7f0e7cec619614902447b1e..6a1df4b150ed131f3691d91d03c3f6a2c2050996 100644
--- a/content/renderer/browser_plugin/browser_plugin.cc
+++ b/content/renderer/browser_plugin/browser_plugin.cc
@@ -495,6 +495,17 @@ bool BrowserPlugin::acceptsInputEvents() {
   return true;
 }
 
+namespace {
+
+bool IsScrollEvent(blink::WebInputEvent::Type event_type) {
+  return event_type == blink::WebInputEvent::GestureScrollBegin ||
+         event_type == blink::WebInputEvent::GestureScrollUpdate ||
+         event_type == blink::WebInputEvent::GestureScrollEnd ||
+         event_type == blink::WebInputEvent::MouseWheel;
+}
+
+}  // namespace
+
 bool BrowserPlugin::handleInputEvent(const blink::WebInputEvent& event,
                                      blink::WebCursorInfo& cursor_info) {
   if (guest_crashed_ || !attached())
@@ -517,7 +528,15 @@ bool BrowserPlugin::handleInputEvent(const blink::WebInputEvent& event,
                                                 view_rect_,
                                                 &event));
   GetWebKitCursorInfo(cursor_, &cursor_info);
-  return true;
+
+  // For scroll events we must block and wait for the response from the guest,
+  // otherwise we do not know if the guest was able to handle the scroll event.
+  // We need to give other elements in the embedder renderer a chance to handle
+  // the scroll if the guest did not.
+  if (IsScrollEvent(event.type))
+    return BrowserPluginManager::Get()->GetScrollHandledStatus();
+  else
+    return true;
 }
 
 bool BrowserPlugin::handleDragStatusUpdate(blink::WebDragStatus drag_status,