[libfuzzer] Add a sanity check for too big images in libpng_read_fuzzer.
[libfuzzer] Add a sanity check for too big images in libpng_read_fuzzer.

This change has been mirrored from google3 png fuzzer. Should prevent some timeouts.

R=aizatsky@chromium.org, inferno@chromium.org, kcc@chromium.org, krasin@chromium.org
BUG=584819
TBR=aizatsky@chromium.org

Review URL: https://codereview.chromium.org/1808123004

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#381749}

axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk