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As is discussed in the bug, it is important to occupy certain
area for logo mark in the home card, otherwise the area for
the search results is restricted.

Actual experimental app-list uses start_page webview for this,
which embeds the logo from our resource data. I think it's better
to create a dummy view with flat background instead of loading
the resource image to emphasize this is still work-in-progress.

BUG=400153
R=oshima@chromium.org
TEST=none

Review URL: https://codereview.chromium.org/441123002

Cr-Commit-Position: refs/heads/master@{#288199}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@288199 0039d316-1c4b-4281-b951-d872f2087c98