Don't send mouse move related events to Cocoa plugins in background windows

webkit/plugins/npapi/webplugin_delegate_impl_mac.mm

 // Copyright (c) 2012 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.
 
 #import <Cocoa/Cocoa.h>
 #import <QuartzCore/QuartzCore.h>
 
 #include "webkit/plugins/npapi/webplugin_delegate_impl.h"
 
 #include <string>
@@ skipping 502 matching lines @@
   // If we get an event before we've set up the plugin, bail.
   if (!have_called_set_window_)
     return false;
 #ifndef NP_NO_CARBON
   if (instance()->event_model() == NPEventModelCarbon &&
       !np_cg_context_.context) {
     return false;
   }
 #endif
 
+  // WebKit sometimes sends spurious mouse move events when the window doesn't
+  // have focus; Cocoa event model plugins don't expect to receive mouse move
+  // events when they are in a background window, so drop those events.
+  if (!containing_window_has_focus_ &&
+      instance()->event_model() == NPEventModelCocoa &&
+      (event.type == WebInputEvent::MouseMove ||
+       event.type == WebInputEvent::MouseEnter ||
+       event.type == WebInputEvent::MouseLeave)) {
+    return false;
+  }
+
   if (WebInputEvent::isMouseEventType(event.type) ||
       event.type == WebInputEvent::MouseWheel) {
     // Check our plugin location before we send the event to the plugin, just
     // in case we somehow missed a plugin frame change.
     const WebMouseEvent* mouse_event =
         static_cast<const WebMouseEvent*>(&event);
     gfx::Point content_origin(
         mouse_event->globalX - mouse_event->x - window_rect_.x(),
         mouse_event->globalY - mouse_event->y - window_rect_.y());
     if (content_origin.x() != content_area_origin_.x() ||
@@ skipping 706 matching lines @@
   qd_manager_->SetFastPathEnabled(enabled);
   qd_port_.port = qd_manager_->port();
   WindowlessSetWindow();
   // Send a paint event so that the new buffer gets updated immediately.
   WindowlessPaint(buffer_context_, clip_rect_);
 }
 #endif  // !NP_NO_QUICKDRAW
 
 }  // namespace npapi
 }  // namespace webkit