[SyncFS] Let container manage FileTracker and FileMetadata ownership

 * Use ScopedPtrHashMap to manage ownership of FileTracker and FileMetadata.
 * Rename FileByID to MetadataByID.
 * Use base::hash_map for std::string keyed containers.

Review URL: https://codereview.chromium.org/173803004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@253385 0039d316-1c4b-4281-b951-d872f2087c98
GVD: Enable high resolution video support on Intel CPU model >= 55.

BUG=346554

Review URL: https://codereview.chromium.org/178153003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@253386 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 253386