Revert of Temporarily disable all calls of CGS private APIs.

ui/views/cocoa/bridged_native_widget.mm

 // Copyright 2014 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 "ui/views/cocoa/bridged_native_widget.h"
 
 #import <objc/runtime.h>
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 67 matching lines @@
 - (void)setCurrentProgress:(NSAnimationProgress)progress {
   [super setCurrentProgress:progress];
   [window_ invalidateShadow];
 }
 @end
 
 namespace {
 
 const CGFloat kMavericksMenuOpacity = 251.0 / 255.0;
 const CGFloat kYosemiteMenuOpacity = 194.0 / 255.0;
-// const int kYosemiteMenuBlur = 80;
+const int kYosemiteMenuBlur = 80;
 
 // Margin at edge and corners of the window that trigger resizing. These match
 // actual Cocoa resize margins.
 const int kResizeAreaEdgeSize = 3;
 const int kResizeAreaCornerSize = 12;
 
 int kWindowPropertiesKey;
 
 float GetDeviceScaleFactorFromView(NSView* view) {
   gfx::Display display =
@@ skipping 1039 matching lines @@
 
   base::scoped_nsobject<CALayer> background_layer([[CALayer alloc] init]);
   [background_layer
       setAutoresizingMask:kCALayerWidthSizable | kCALayerHeightSizable];
 
   if (widget_type_ == Widget::InitParams::TYPE_MENU) {
     // Giving the canvas opacity messes up subpixel font rendering, so use a
     // solid background, but make the CALayer transparent.
     if (base::mac::IsOSYosemiteOrLater()) {
       [background_layer setOpacity:kYosemiteMenuOpacity];
-
-      // TODO(erikchen): Temporarily disabled. https://crbug.com/515627.
-      // CGSSetWindowBackgroundBlurRadius(
-      //     _CGSDefaultConnection(), [window_ windowNumber],
-      //     kYosemiteMenuBlur);
+      CGSSetWindowBackgroundBlurRadius(
+          _CGSDefaultConnection(), [window_ windowNumber], kYosemiteMenuBlur);
       // The blur effect does not occur with a fully transparent (or fully
       // layer-backed) window. Setting a window background will use square
       // corners, so ask the contentView to draw one instead.
       [bridged_view_ setDrawMenuBackgroundForBlur:YES];
     } else {
       [background_layer setOpacity:kMavericksMenuOpacity];
     }
   }
 
   // Set the layer first to create a layer-hosting view (not layer-backed).
@@ skipping 78 matching lines @@
   [bridged_view_ setMouseDownCanMoveWindow:draggable];
   // AppKit will not update its cache of mouseDownCanMoveWindow unless something
   // changes. Previously we tried adding an NSView and removing it, but for some
   // reason it required reposting the mouse-down event, and didn't always work.
   // Calling the below seems to be an effective solution.
   [window_ setMovableByWindowBackground:NO];
   [window_ setMovableByWindowBackground:YES];
 }
 
 }  // namespace views