[Picture in Picture] Disable context menu PIP command.

This is temporary while PIP is being wired up and worked to be more
stable through the media controls entry point.

The menu item is not removed because we intend to continue using it
and it is currently hidden behind a flag.

BUG: 817598
Change-Id: I9156d81b40dd6c97e19c6eef3f5fbbe13e350639
Reviewed-on: https://chromium-review.googlesource.com/942305
Commit-Queue: apacible <apacible@chromium.org>
Reviewed-by: Istiaque Ahmed <lazyboy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#540246}

chrome/browser/renderer_context_menu/render_view_context_menu.cc

@@ -2614,10 +2614,10 @@ void RenderViewContextMenu::ExecPictureInPicture() {
   if (!base::FeatureList::IsEnabled(media::kPictureInPicture))
     return;
 
-  PictureInPictureWindowController* window_controller =
-      PictureInPictureWindowController::GetOrCreateForWebContents(
-          embedder_web_contents_);
-  window_controller->Show();
+  // TODO(apacible): Re-enable contextual menu entry point for
+  // Picture-in-Picture after end to end flow through the media controls is
+  // stable. http://crbug/817613.
+  NOTIMPLEMENTED();
 }
 
 void RenderViewContextMenu::WriteURLToClipboard(const GURL& url) {