[Mac] Add testing code to expose an NSColor memory leak.

chrome/browser/cocoa/cocoa_test_helper.mm

+// Copyright (c) 2009 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/cocoa/cocoa_test_helper.h"
+
+@implementation CocoaTestHelperWindow
+
+- (id)initWithContentRect:(NSRect)contentRect {
+  return [self initWithContentRect:contentRect
+                         styleMask:NSBorderlessWindowMask
+                           backing:NSBackingStoreBuffered
+                             defer:NO];
+}
+
+- (id)init {
+  return [self initWithContentRect:NSMakeRect(0, 0, 800, 600)];
+}
+
+- (void)setPretendIsKeyWindow:(BOOL)flag {
+  pretendIsKeyWindow_ = flag;
+}
+
+- (BOOL)isKeyWindow {
+  return pretendIsKeyWindow_;
+}
+
+@end