Back out r240455 on the trunk. It caused http://crbug.com/328776.

trunk/src/chrome/browser/ui/cocoa/extensions/extension_popup_controller.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 "chrome/browser/ui/cocoa/extensions/extension_popup_controller.h"
 
 #include <algorithm>
 
 #include "base/callback.h"
 #include "chrome/browser/chrome_notification_types.h"
@@ skipping 322 matching lines @@
   // positioned correctly at the middle and slightly down from the button.
   NSPoint windowOrigin = self.anchorPoint;
   NSSize offsets = NSMakeSize(info_bubble::kBubbleArrowXOffset +
                                   info_bubble::kBubbleArrowWidth / 2.0,
                               info_bubble::kBubbleArrowHeight / 2.0);
   offsets = [extensionView_ convertSize:offsets toView:nil];
   windowOrigin.x -= NSWidth(frame) - offsets.width;
   windowOrigin.y -= NSHeight(frame) - offsets.height;
   frame.origin = windowOrigin;
 
-  // In case the window is animating already, change its size by creating a
-  // new animation setting the opacity and new frame value. Otherwise, a
-  // preexisting animation would continue after the frame is set, reverting
-  // the frame to what it was when the animation started.
+  // Is the window still animating in? If so, then cancel that and create a new
+  // animation setting the opacity and new frame value. Otherwise the current
+  // animation will continue after this frame is set, reverting the frame to
+  // what it was when the animation started.
   NSWindow* window = [self window];
-  id animator = [window animator];
-  [NSAnimationContext beginGrouping];
-  [[NSAnimationContext currentContext] setDuration:kAnimationDuration];
-  [animator setAlphaValue:1.0];
-  [animator setFrame:frame display:YES];
-  [NSAnimationContext endGrouping];
+  if ([window isVisible] && [[window animator] alphaValue] < 1.0) {
+    [NSAnimationContext beginGrouping];
+    [[NSAnimationContext currentContext] setDuration:kAnimationDuration];
+    [[window animator] setAlphaValue:1.0];
+    [[window animator] setFrame:frame display:YES];
+    [NSAnimationContext endGrouping];
+  } else {
+    [window setFrame:frame display:YES];
+  }
 
   // A NSViewFrameDidChangeNotification won't be sent until the extension view
   // content is loaded. The window is hidden on init, so show it the first time
   // the notification is fired (and consequently the view contents have loaded).
   if (![window isVisible]) {
     [self showWindow:self];
   }
 }
 
 - (void)onSizeChanged:(NSSize)newSize {
@@ skipping 42 matching lines @@
   return minSize;
 }
 
 // Private (TestingAPI)
 + (NSSize)maxPopupSize {
   NSSize maxSize = {ExtensionViewMac::kMaxWidth, ExtensionViewMac::kMaxHeight};
   return maxSize;
 }
 
 @end