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The goal is to list the top domains that show non-real icons and then
debug them individually. If we find evidence that such domains do
actually provide large icons, it would suggest there's client-side bugs
that prevent from displaying this icon (either it wasn't fetched, the
wrong version was kept around, it was garbage-collected, etc.).

BUG=672411

Review-Url: https://codereview.chromium.org/2557513007
Cr-Commit-Position: refs/heads/master@{#437838}