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This CL adds a basic version of a start page to the experimental app list.
This page contains a WebView that displays the Google Logo and a grey bar
which are currently only placeholders.

This CL also modifies the StartPage WebUI to have the google logo.

BUG=349727

Review URL: https://codereview.chromium.org/186483004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@269752 0039d316-1c4b-4281-b951-d872f2087c98