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This adds a LayerImpl::ValidateQuadResources() that each layer can
call on quads that it appends. This function is empty when DCHECKs are
off, which means it should be cheap/free in release builds.

R=piman@chromium.org
BUG=475894

Review URL: https://codereview.chromium.org/1096703006

Cr-Commit-Position: refs/heads/master@{#326903}