[Mac] Fix some leaks in tab drawing code.

chrome/browser/ui/cocoa/tabs/tab_view.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/tabs/tab_view.h"
 
 #include "base/logging.h"
 #include "base/mac/sdk_forward_declarations.h"
 #include "chrome/browser/themes/theme_service.h"
 #import "chrome/browser/ui/cocoa/nsview_additions.h"
@@ skipping 665 matching lines @@
   NSImage* leftMask = rb.GetNativeImageNamed(IDR_TAB_ALPHA_LEFT).ToNSImage();
   NSImage* rightMask = rb.GetNativeImageNamed(IDR_TAB_ALPHA_RIGHT).ToNSImage();
 
   CGFloat leftWidth = leftMask.size.width;
   CGFloat rightWidth = rightMask.size.width;
 
   // Image masks must be in the DeviceGray colorspace. Create a context and
   // draw the mask into it.
   base::ScopedCFTypeRef<CGColorSpaceRef> colorspace(
       CGColorSpaceCreateDeviceGray());
-  CGContextRef maskContext =
+  base::ScopedCFTypeRef<CGContextRef> maskContext(

[Nico, 2013/09/16 20:54:21]

!!

       CGBitmapContextCreate(NULL, tabWidth * scale, kMaskHeight * scale,
-                            8, tabWidth * scale, colorspace, 0);
+                            8, tabWidth * scale, colorspace, 0));
   CGContextScaleCTM(maskContext, scale, scale);
   NSGraphicsContext* maskGraphicsContext =
       [NSGraphicsContext graphicsContextWithGraphicsPort:maskContext
                                                  flipped:NO];
 
   gfx::ScopedNSGraphicsContextSaveGState scopedGState;
   [NSGraphicsContext setCurrentContext:maskGraphicsContext];
 
   // Draw mask image.
   [[NSColor blackColor] setFill];
   CGContextFillRect(maskContext, CGRectMake(0, 0, tabWidth, kMaskHeight));
 
   NSDrawThreePartImage(NSMakeRect(0, 0, tabWidth, kMaskHeight),
       leftMask, nil, rightMask, /*vertical=*/NO, NSCompositeSourceOver, 1.0,
       /*flipped=*/NO);
 
   CGFloat middleWidth = tabWidth - leftWidth - rightWidth;
   NSRect middleRect = NSMakeRect(leftWidth, 0, middleWidth, kFillHeight);
   [[NSColor whiteColor] setFill];
   NSRectFill(middleRect);
 
   maskCache_.reset(CGBitmapContextCreateImage(maskContext));
   return maskCache_;
 }
 
 @end  // @implementation TabView(Private)