Check for no pixels after calling lockPixels(). If so, we return rather than

Check for no pixels after calling lockPixels(). If so, we return rather than
dereferencing null.

http://code.google.com/p/chromium/issues/detail?id=79369
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=86442

[brettw, 2011-05-24 15:52:50]

LGTM