Throttle the touch move events sent to the renderer.

content/browser/renderer_host/render_widget_host.h

 // Copyright (c) 2011 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.
 
 #ifndef CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_H_
 #define CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_H_
 #pragma once
 
 #include <deque>
 #include <string>
@@ skipping 572 matching lines @@
 
   // (Similar to |next_mouse_move_|.) The next mouse wheel events to send.
   // Unlike mouse moves, mouse wheel events received while one is pending are
   // coalesced (by accumulating deltas) if they match the previous event in
   // modifiers. On the Mac, in particular, mouse wheel events are received at a
   // high rate; not waiting for the ack results in jankiness, and using the same
   // mechanism as for mouse moves (just dropping old events when multiple ones
   // would be queued) results in very slow scrolling.
   WheelEventQueue coalesced_mouse_wheel_events_;
 
+#if defined(TOUCH_UI)
+  // True if a touch move event was sent to the renderer view and we are waiting
+  // for a corresponding ACK message.
+  bool touch_move_pending_;
+
+  // If a touch move event comes in while we are waiting for an ACK for a
+  // previously sent touch move event, it will be stored here. A touch event
+  // stores the location of the moved point, instead of the amount that it
+  // moved. So it is not necessary to coalesce the move events (as is done for
+  // mouse wheel events). Storing the most recent event for dispatch is
+  // sufficient.
+  WebKit::WebTouchEvent queued_touch_event_;
+  bool touch_event_is_queued_;
+#endif
+
   // The time when an input event was sent to the RenderWidget.
   base::TimeTicks input_event_start_time_;
 
   // If true, then we should repaint when restoring even if we have a
   // backingstore.  This flag is set to true if we receive a paint message
   // while is_hidden_ to true.  Even though we tell the render widget to hide
   // itself, a paint message could already be in flight at that point.
   bool needs_repainting_on_restore_;
 
   // This is true if the renderer is currently unresponsive.
@@ skipping 53 matching lines @@
 
   std::vector<gfx::PluginWindowHandle> deferred_plugin_handles_;
 
   // The last scroll offset of the render widget.
   gfx::Point last_scroll_offset_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderWidgetHost);
 };
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_H_