Add missed NULL check in r274802

TBR=miu
BUG=381542

Review URL: https://codereview.chromium.org/319183003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@275525 0039d316-1c4b-4281-b951-d872f2087c98

content/browser/renderer_host/render_widget_host_view_mac.mm

@@ -2524,6 +2524,9 @@ void RenderWidgetHostViewMac::BrowserCompositorDidDrawFrame() {
 // CompositingIOSurfaceLayerClient, public:
 
 void RenderWidgetHostViewMac::AcceleratedLayerDidDrawFrame(bool succeeded) {
+  if (!render_widget_host_)
+    return;
+
   SendPendingLatencyInfoToHost();
   SendPendingSwapAck();
   if (!succeeded)