Always call the class methods to save/restore contexts.

ui/gfx/scoped_ns_graphics_context_save_gstate_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/gfx/scoped_ns_graphics_context_save_gstate_mac.h"
 
-#include <AppKit/AppKit.h>
+#import <AppKit/AppKit.h>
+
+#include "base/logging.h"
+#include "base/mac/mac_util.h"
 
 namespace gfx {
 
-ScopedNSGraphicsContextSaveGState::ScopedNSGraphicsContextSaveGState(
-    NSGraphicsContext* context) : context_([context retain]) {
-  if (!context_)
-    context_.reset([[NSGraphicsContext currentContext] retain]);
-  [context_ saveGraphicsState];
+ScopedNSGraphicsContextSaveGState::ScopedNSGraphicsContextSaveGState()
+    : context_([NSGraphicsContext currentContext]) {
+  [NSGraphicsContext saveGraphicsState];
 }
 
 ScopedNSGraphicsContextSaveGState::~ScopedNSGraphicsContextSaveGState() {
-  [context_ restoreGraphicsState];
+  [NSGraphicsContext restoreGraphicsState];
+  if (!context_ && base::mac::IsOSLeopardOrEarlier()) {
+    // On 10.5 and earlier, there is a bug. If the current graphics context was
+    // nil when +[NSGraphicsContext saveGraphicsState] was called, then calling
+    // +[NSGraphicsContext restoreGraphicsState] will not restore a nil current
+    // context, but will leave the current context in place. Because allowing
+    // that stale context (which is likely been dealloced) to remain current

[Mark Mentovai, 2011/08/05 22:11:32]

(which is likely to be dealloced)

+    // will only lead to heartache and pain, the current context must be
+    // manually nilled out.
+    [NSGraphicsContext setCurrentContext:nil];
+  }
+  DCHECK_EQ(context_, [NSGraphicsContext currentContext]);
 }
 
 }  // namespace gfx