Fix crashes due to gfx::Image unsafe thread passing

gfx::Image has |storage_| member which is base::RefCounted, not thread
safe. Thus passing around gfx::Image to other threads by copying is
incorrect.

Workaround by using scoped_ptr and making ImageRecord class
RefCountedThreadSafe.

Related discussion:
https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/8LqVoXQ_2bo

BUG=471800

Review URL: https://codereview.chromium.org/1031293002

Cr-Commit-Position: refs/heads/master@{#323720}
17 files changed