Validate Bucket data in ShaderSourceBucket.

As of now only the received bucket and
the size of bucket are validated. We
should check for validation of bucket
data before we start using it and report
failures.

BUG= 240467

Review URL: https://codereview.chromium.org/822953002

Cr-Commit-Position: refs/heads/master@{#309882}
2 files changed