Revert of Temporarily disable all calls of CGS private APIs.

ui/views/cocoa/bridged_native_widget.mm

Index: ui/views/cocoa/bridged_native_widget.mm
diff --git a/ui/views/cocoa/bridged_native_widget.mm b/ui/views/cocoa/bridged_native_widget.mm
index a2ce9bd6b07916f17014286b87e8b77ed1f09f18..6f5dec0f96864ede56c8a7cf940de5ebf964aa92 100644
--- a/ui/views/cocoa/bridged_native_widget.mm
+++ b/ui/views/cocoa/bridged_native_widget.mm
@@ -85,7 +85,7 @@
 
 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.
@@ -1145,11 +1145,8 @@
     // 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.