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This CL improves the code quality in VideoResourceUpdater.
1. Use C++11/14 conventions if possible.
2. Use OnceCallback and use member functions.
2. Delete dead code.
3. Add comments.

Bug: 730660
Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel;master.tryserver.chromium.android:android_optional_gpu_tests_rel
Change-Id: I6d34839b7b781fa61b3b7c6655f7bba599892755
Reviewed-on: https://chromium-review.googlesource.com/959046
Commit-Queue: kylechar <kylechar@chromium.org>
Reviewed-by: danakj <danakj@chromium.org>
Cr-Commit-Position: refs/heads/master@{#544131}