Don't RAF align touch moves that are blocking.

content/renderer/input/main_thread_event_queue.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/renderer/input/main_thread_event_queue.h"
 
 #include "base/metrics/histogram_macros.h"
 #include "content/common/input/event_with_latency_info.h"
 #include "content/common/input_messages.h"
 
 namespace content {
 
 namespace {
 
 // The maximum number of post-coalesced events processed per rAF task. 10 was
 // chosen because it really should never be hit yet prevents an infinite loop if
 // the compositor keeps delivering events faster than the main thread can
 // process them.
 const size_t kMaxEventsPerRafTask = 10;
 
 const size_t kTenSeconds = 10 * 1000 * 1000;
 
 bool isContinuousEvent(const std::unique_ptr<EventWithDispatchType>& event) {
   switch (event->event().type) {
     case blink::WebInputEvent::MouseMove:
-    case blink::WebInputEvent::TouchMove:
     case blink::WebInputEvent::MouseWheel:
       return true;
+    case blink::WebInputEvent::TouchMove:
+      // TouchMoves that are blocking end up blocking scroll. Do not treat
+      // them as continuous events otherwise we will end up waiting up to an
+      // additional frame.
+      return static_cast<const blink::WebTouchEvent&>(event->event())
+                 .dispatchType != blink::WebInputEvent::Blocking;
     default:
       return false;
   }
 }
 
 }  // namespace
 
 EventWithDispatchType::EventWithDispatchType(
     ui::ScopedWebInputEvent event,
     const ui::LatencyInfo& latency,
@@ skipping 240 matching lines @@
       }
     }
   }
   for (size_t i = 0; i < send_notification_count; ++i)
     SendEventNotificationToMainThread();
   if (needs_main_frame)
     client_->NeedsMainFrame(routing_id_);
 }
 
 }  // namespace content