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This patch ensures that we don't even try to checker images that are
too big to fit into our cache.

R=khushalsagar@chromium.org
CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel

Review-Url: https://codereview.chromium.org/2844273004
Cr-Commit-Position: refs/heads/master@{#468186}