Allow BlobDataHandles to be copied, and have their UUIDs read, on any thread.

BUG=108012

Review URL: https://codereview.chromium.org/259773006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@266817 0039d316-1c4b-4281-b951-d872f2087c98
4 files changed