Always call the class methods to save/restore contexts.

ui/gfx/scoped_ns_graphics_context_save_gstate_mac.mm

Index: ui/gfx/scoped_ns_graphics_context_save_gstate_mac.mm
diff --git a/ui/gfx/scoped_ns_graphics_context_save_gstate_mac.mm b/ui/gfx/scoped_ns_graphics_context_save_gstate_mac.mm
index f3992ea0b694a520c9b45b869151144d4237836b..a6be99b66cda126409937d9f6832fa0370395bd9 100644
--- a/ui/gfx/scoped_ns_graphics_context_save_gstate_mac.mm
+++ b/ui/gfx/scoped_ns_graphics_context_save_gstate_mac.mm
@@ -4,19 +4,16 @@
 
 #include "ui/gfx/scoped_ns_graphics_context_save_gstate_mac.h"
 
-#include <AppKit/AppKit.h>
+#import <AppKit/AppKit.h>
 
 namespace gfx {
 
-ScopedNSGraphicsContextSaveGState::ScopedNSGraphicsContextSaveGState(
-    NSGraphicsContext* context) : context_([context retain]) {
-  if (!context_)
-    context_.reset([[NSGraphicsContext currentContext] retain]);
-  [context_ saveGraphicsState];
+ScopedNSGraphicsContextSaveGState::ScopedNSGraphicsContextSaveGState() {
+  [NSGraphicsContext saveGraphicsState];
 }
 
 ScopedNSGraphicsContextSaveGState::~ScopedNSGraphicsContextSaveGState() {
-  [context_ restoreGraphicsState];
+  [NSGraphicsContext restoreGraphicsState];
 }
 
 }  // namespace gfx