Defer synthetic gesture completions until events have been flushed

content/browser/renderer_host/input/synthetic_gesture_controller.cc

Index: content/browser/renderer_host/input/synthetic_gesture_controller.cc
diff --git a/content/browser/renderer_host/input/synthetic_gesture_controller.cc b/content/browser/renderer_host/input/synthetic_gesture_controller.cc
index 57b3af0e1af0cbcf40d8dd7122fb16e3b5067f4b..8314d948ba751c5776816c29fc3c86dd567c2700 100644
--- a/content/browser/renderer_host/input/synthetic_gesture_controller.cc
+++ b/content/browser/renderer_host/input/synthetic_gesture_controller.cc
@@ -36,16 +36,34 @@ void SyntheticGestureController::Flush(base::TimeTicks timestamp) {
   if (pending_gesture_queue_.IsEmpty())
     return;
 
+  if (pending_gesture_result_)
+    return;
+
   SyntheticGesture* gesture = pending_gesture_queue_.FrontGesture();
-  SyntheticGesture::Result result = gesture->ForwardInputEvents(timestamp,
-      gesture_target_.get());
+  SyntheticGesture::Result result =
+      gesture->ForwardInputEvents(timestamp, gesture_target_.get());
 
   if (result == SyntheticGesture::GESTURE_RUNNING) {
     gesture_target_->SetNeedsFlush();
     return;
   }
 
-  StopGesture(*gesture, pending_gesture_queue_.FrontCallback(), result);
+  // It's possible that all events generated by the gesture have been fully
+  // dispatched at this point, in which case |OnDidFlushInput()| was called
+  // before |pending_gesture_result_| was initialized. Requesting another flush
+  // will trigger the necessary gesture-ending call to |OnDidFlushInput()|.
+  pending_gesture_result_.reset(new SyntheticGesture::Result(result));
+  gesture_target_->SetNeedsFlush();
+}
+
+void SyntheticGestureController::OnDidFlushInput() {
+  if (!pending_gesture_result_)
+    return;
+
+  DCHECK(!pending_gesture_queue_.IsEmpty());
+  StopGesture(*pending_gesture_queue_.FrontGesture(),
+              pending_gesture_queue_.FrontCallback(),
+              *pending_gesture_result_.Pass());
   pending_gesture_queue_.Pop();
 
   if (!pending_gesture_queue_.IsEmpty())