Fix dummy plugin window update (Mac)

webkit/glue/plugins/webplugin_delegate_impl_mac.mm

 // Copyright (c) 2006-2008 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>
 
 #include "webkit/glue/plugins/webplugin_delegate_impl.h"
 
 #include <string>
 #include <vector>
@@ skipping 305 matching lines @@
 // If new_width or new_height is non-zero, the window size (content region)
 // will be updated accordingly; if they are zero, the existing size will be
 // preserved.
 static void UpdateDummyWindowBoundsWithOffset(WindowRef window,
                                               int x_offset, int y_offset,
                                               int new_width, int new_height) {
   int target_x = g_current_x_offset + x_offset;
   int target_y = g_current_y_offset + y_offset;
   Rect window_bounds;
   GetWindowBounds(window, kWindowContentRgn, &window_bounds);
-  if ((window_bounds.left != target_x) ||
-      (window_bounds.top != target_y)) {
-    int height = new_height ? new_height
-                            : window_bounds.bottom - window_bounds.top;
-    int width = new_width ? new_width
-                          : window_bounds.right - window_bounds.left;
+  int old_width = window_bounds.right - window_bounds.left;
+  int old_height = window_bounds.bottom - window_bounds.top;
+  if (window_bounds.left != target_x ||
+      window_bounds.top != target_y ||
+      (new_width && new_width != old_width) ||
+      (new_height && new_height != old_height)) {
+    int height = new_height ? new_height : old_height;
+    int width = new_width ? new_width : old_width;
     window_bounds.left = target_x;
     window_bounds.top = target_y;
     window_bounds.right = window_bounds.left + width;
     window_bounds.bottom = window_bounds.top + height;
     SetWindowBounds(window, kWindowContentRgn, &window_bounds);
   }
 }
 
 void WebPluginDelegateImpl::WindowlessSetWindow(bool force_set_window) {
   if (!instance())
@@ skipping 393 matching lines @@
 
 #ifndef NP_NO_CARBON
   if (instance_->event_model() == NPEventModelCarbon) {
     MessageLoop::current()->PostDelayedTask(FROM_HERE,
         null_event_factory_.NewRunnableMethod(
             &WebPluginDelegateImpl::OnNullEvent),
         kPluginIdleThrottleDelayMs);
   }
 #endif
 }