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

trunk/src/chrome/browser/ui/cocoa/extensions/extension_popup_controller.mm

Index: trunk/src/chrome/browser/ui/cocoa/extensions/extension_popup_controller.mm
===================================================================
--- trunk/src/chrome/browser/ui/cocoa/extensions/extension_popup_controller.mm	(revision 240945)
+++ trunk/src/chrome/browser/ui/cocoa/extensions/extension_popup_controller.mm	(working copy)
@@ -340,17 +340,20 @@
   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