Send the pending input event ack before the UpdateRect message

content/renderer/render_widget.cc

 // 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.
 
 #include "content/renderer/render_widget.h"
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/debug/trace_event.h"
 #include "base/logging.h"
@@ skipping 429 matching lines @@
   if (!message.ReadData(&iter, &data, &data_length)) {
     handling_input_event_ = false;
     return;
   }
 
   const WebInputEvent* input_event =
       reinterpret_cast<const WebInputEvent*>(data);
 
   bool prevent_default = false;
   if (WebInputEvent::isMouseEventType(input_event->type)) {
+    TRACE_EVENT2("renderer", "HandleMouseMove",

[darin (slow to review), 2011/12/06 23:19:48]

nit: maybe this code would be cleaner with a local variable:

  const WebMouseEvent* mouse_event =
      static_cast<...>(...);
  TRACE_EVENT2(...
               "x", mouse_event->x,
               "y", mouse_event->y);
  prevent_default = WillHandleMouseEvent(*mouse_event);

+                 "x", static_cast<const WebMouseEvent*>(input_event)->x,
+                 "y", static_cast<const WebMouseEvent*>(input_event)->y);
     prevent_default = WillHandleMouseEvent(
         *(static_cast<const WebMouseEvent*>(input_event)));
   }
 
   bool processed = prevent_default;
   if (!processed && webwidget_)
     processed = webwidget_->handleInputEvent(*input_event);
 
   IPC::Message* response =
       new ViewHostMsg_HandleInputEvent_ACK(routing_id_, input_event->type,
@@ skipping 372 matching lines @@
   } else {
     params.scroll_rect = update.scroll_rect;
     params.copy_rects.swap(copy_rects);  // TODO(darin): clip to bounds?
   }
   params.view_size = size_;
   params.resizer_rect = resizer_rect_;
   params.plugin_window_moves.swap(plugin_window_moves_);
   params.flags = next_paint_flags_;
   params.scroll_offset = GetScrollOffset();
 
+  if (pending_input_event_ack_.get())

[darin (slow to review), 2011/12/06 23:19:48]

This probably deserves a comment.

+    Send(pending_input_event_ack_.release());
+
   update_reply_pending_ = true;
   Send(new ViewHostMsg_UpdateRect(routing_id_, params));
   next_paint_flags_ = 0;
 
   UpdateTextInputState();
   UpdateSelectionBounds();
 
   // Let derived classes know we've painted.
   DidInitiatePaint();
 }
@@ skipping 636 matching lines @@
   }
 }
 
 bool RenderWidget::WillHandleMouseEvent(const WebKit::WebMouseEvent& event) {
   return false;
 }
 
 bool RenderWidget::WebWidgetHandlesCompositorScheduling() const {
   return false;
 }