Remove unused definitions.

Their use was removed in 6c0aed57.

BUG=829347

Change-Id: Ia5e99e49ba53cb4a416fda37407fdf5faa516f27
Reviewed-on: https://chromium-review.googlesource.com/1156845Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Commit-Queue: Avi Drissman <avi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#579440}

ui/views/cocoa/bridged_native_widget.mm

@@ -43,15 +43,6 @@
 #include "ui/views/widget/widget_delegate.h"
 #include "ui/views/window/dialog_delegate.h"
 
-extern "C" {
-
-typedef int32_t CGSConnection;
-CGSConnection _CGSDefaultConnection();
-CGError CGSSetWindowBackgroundBlurRadius(CGSConnection connection,
-                                         NSInteger windowNumber,
-                                         int radius);
-
-}
 namespace {
 constexpr auto kUIPaintTimeout = base::TimeDelta::FromSeconds(5);
 }  // namespace