Delegate root layer scroll offset to android_webview.

content/renderer/gpu/input_handler_manager.cc

Index: content/renderer/gpu/input_handler_manager.cc
diff --git a/content/renderer/gpu/input_handler_manager.cc b/content/renderer/gpu/input_handler_manager.cc
index ef6bc3f1357113904a54f24e641a48048e0a19ca..4507d7d0eac221bb001a8f97470428c7d9c7a0fb 100644
--- a/content/renderer/gpu/input_handler_manager.cc
+++ b/content/renderer/gpu/input_handler_manager.cc
@@ -91,6 +91,29 @@ void InputHandlerManager::AddInputHandlerOnCompositorThread(
           routing_id, main_loop, input_handler, render_view_impl));
 }
 
+void InputHandlerManager::SetRootLayerScrollDelegate(
+      int routing_id,
+      cc::LayerScrollOffsetDelegate* root_layer_scroll_offset_delegate) {
+  message_loop_proxy_->PostTask(
+      FROM_HERE,
+      base::Bind(
+          &InputHandlerManager::SetRootLayerScrollDelegateOnCompositorThread,
+          base::Unretained(this),
+          routing_id,
+          base::Unretained(root_layer_scroll_offset_delegate)));
+}
+
+void InputHandlerManager::SetRootLayerScrollDelegateOnCompositorThread(
+      int routing_id,
+      cc::LayerScrollOffsetDelegate* root_layer_scroll_offset_delegate) {
+  if (input_handlers_.count(routing_id) == 0) {
+    DCHECK(false);
+    return;
+  }
+  input_handlers_[routing_id]->input_handler_proxy()
+      ->SetRootLayerScrollOffsetDelegate(root_layer_scroll_offset_delegate);
+}
+
 void InputHandlerManager::RemoveInputHandler(int routing_id) {
   DCHECK(message_loop_proxy_->BelongsToCurrentThread());