MacViews: Fix failing mouse capture unittests.

ui/views/test/event_generator_delegate_mac.mm

 // Copyright 2014 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 <stddef.h>
 
 #import "base/mac/scoped_nsobject.h"
 #import "base/mac/scoped_objc_class_swizzler.h"
 #include "base/macros.h"
@@ skipping 410 matching lines @@
 
 gfx::Point EventGeneratorDelegateMac::CenterOfTarget(
     const ui::EventTarget* target) const {
   DCHECK_EQ(target, this);
   return CenterOfWindow(window_);
 }
 
 gfx::Point EventGeneratorDelegateMac::CenterOfWindow(
     gfx::NativeWindow window) const {
   DCHECK_EQ(window, window_);
-  return gfx::ScreenRectFromNSRect([window frame]).CenterPoint();
+  // Assume the window is at the top-left of the coordinate system (even if
+  // AppKit has moved it into the work area) see ConvertRootPointToTarget().
+  return gfx::Point(NSWidth([window frame]) / 2, NSHeight([window frame]) / 2);
 }
 
 // Return the current owner of the EventGeneratorDelegate. May be null.
 ui::test::EventGenerator* GetActiveGenerator() {
   return EventGeneratorDelegateMac::GetInstance()->owner();
 }
 
 }  // namespace
 
 namespace views {
@@ skipping 47 matching lines @@
 - (NSEvent*)currentEvent {
   if (g_current_event)
     return g_current_event;
 
   // Find the original implementation and invoke it.
   IMP original = EventGeneratorDelegateMac::GetInstance()->CurrentEventMethod();
   return original(self, _cmd);
 }
 
 @end