Remove "Search Google for this image" context menu item for <webview>.

The functionality was always broken, so remove it until it gets fixed.
We already do not show Searh google for * keyword item anyway.

BUG=407897
Test=In a chrome app, open a <webview> that loads an image.
Right click on that image.
"Search Google for this image" context menu item shouldn't appear.

Review URL: https://codereview.chromium.org/523023003

Cr-Commit-Position: refs/heads/master@{#292749}
1 file changed