Always call the class methods to save/restore contexts.

ui/base/clipboard/clipboard_mac.mm

 // Copyright (c) 2011 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.
 
 #include "ui/base/clipboard/clipboard.h"
 
 #import <Cocoa/Cocoa.h>
 
 #include "base/file_path.h"
 #include "base/logging.h"
 #include "base/mac/mac_util.h"
 #include "base/mac/scoped_cftyperef.h"
 #include "base/memory/scoped_nsobject.h"
 #include "base/sys_string_conversions.h"
 #include "base/utf_string_conversions.h"
 #import "third_party/mozilla/NSPasteboard+Utils.h"
 #include "third_party/skia/include/core/SkBitmap.h"
 #include "ui/gfx/canvas_skia.h"
+#include "ui/gfx/scoped_ns_graphics_context_save_gstate_mac.h"
 #include "ui/gfx/size.h"
 
 namespace ui {
 
 namespace {
 
 // Would be nice if this were in UTCoreTypes.h, but it isn't
 NSString* const kUTTypeURLName = @"public.url-name";
 
 // Tells us if WebKit was the last to write to the pasteboard. There's no
@@ skipping 212 matching lines @@
   if (src_url)
     src_url->clear();
 }
 
 SkBitmap Clipboard::ReadImage(Buffer buffer) const {
   DCHECK_EQ(buffer, BUFFER_STANDARD);
 
   scoped_nsobject<NSImage> image(
       [[NSImage alloc] initWithPasteboard:GetPasteboard()]);
   if (image.get()) {
+    gfx::ScopedNSGraphicsContextSaveGState scoped_state;
     [image setFlipped:YES];
     int width = [image size].width;
     int height = [image size].height;
 
     gfx::CanvasSkia canvas(width, height, false);
     skia::ScopedPlatformPaint scoped_platform_paint(&canvas);
     CGContextRef gc = scoped_platform_paint.GetPlatformSurface();
     NSGraphicsContext* cocoa_gc =
         [NSGraphicsContext graphicsContextWithGraphicsPort:gc flipped:NO];
     [NSGraphicsContext setCurrentContext:cocoa_gc];

[Mark Mentovai, 2011/08/05 01:15:45]

☞

     [image drawInRect:NSMakeRect(0, 0, width, height)
              fromRect:NSZeroRect
             operation:NSCompositeCopy
              fraction:1.0];
-    [NSGraphicsContext restoreGraphicsState];
     return canvas.ExtractBitmap();
   }
   return SkBitmap();
 }
 
 void Clipboard::ReadBookmark(string16* title, std::string* url) const {
   NSPasteboard* pb = GetPasteboard();
 
   if (title) {
     NSString* contents = [pb stringForType:kUTTypeURLName];
@@ skipping 99 matching lines @@
 }
 
 // static
 Clipboard::FormatType Clipboard::GetWebKitSmartPasteFormatType() {
   static const std::string type =
       base::SysNSStringToUTF8(kWebSmartPastePboardType);
   return type;
 }
 
 }  // namespace ui