Specialize reporting of Media.GpuVideoDecoderInitializeStatus UMA to comply with API requirements.

CreateUMAReportingPipelineCB encouraged abuse of the UMA API in that it accepted
a "name" parameter even though the UMA_HISTOGRAM_* macros must always be called
with the same name from each call-site.  Replaced the only call-site with a
specialized version to avoid future bugs.

Review URL: https://codereview.chromium.org/81313002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@236701 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 236701
Making cast run on multi thread

1. Switching weak_ptr->unretained(this) which allows switching betwen threads. 
2. Adding thread DCHECKS

Review URL: https://codereview.chromium.org/81353002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@236702 0039d316-1c4b-4281-b951-d872f2087c98
Check result of fwrite() to avoid compiler warning

Affects compiling unittests for ChromeOS target.

BUG=None
TEST=local build for CrOS snow

Review URL: https://codereview.chromium.org/81393003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@236703 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 236703