Rewrite most of the scopers in //base/mac to use ScopedTypeRef or ScopedGeneric.

ui/gl/scoped_cgl.h

Index: ui/gl/scoped_cgl.h
diff --git a/ui/gl/scoped_cgl.h b/ui/gl/scoped_cgl.h
index 071b65872166cd0f1f3be6656aab6b82f07bbe5c..860a7568c1d16b191b3e766f15498f481ad0f501 100644
--- a/ui/gl/scoped_cgl.h
+++ b/ui/gl/scoped_cgl.h
@@ -16,8 +16,8 @@ namespace base {
 template<>
 struct ScopedTypeRefTraits<CGLContextObj> {
   static CGLContextObj InvalidValue() { return nullptr; }
-  static void Retain(CGLContextObj object) {
-    CGLRetainContext(object);
+  static CGLContextObj Retain(CGLContextObj object) {
+    return CGLRetainContext(object);
   }
   static void Release(CGLContextObj object) {
     CGLReleaseContext(object);
@@ -27,8 +27,8 @@ struct ScopedTypeRefTraits<CGLContextObj> {
 template<>
 struct ScopedTypeRefTraits<CGLPixelFormatObj> {
   static CGLPixelFormatObj InvalidValue() { return nullptr; }
-  static void Retain(CGLPixelFormatObj object) {
-    CGLRetainPixelFormat(object);
+  static CGLPixelFormatObj Retain(CGLPixelFormatObj object) {
+    return CGLRetainPixelFormat(object);
   }
   static void Release(CGLPixelFormatObj object) {
     CGLReleasePixelFormat(object);