[cros] RlzValueStore made protected by a cross-process lock and not persisted over browser lifetime (like on Mac).

*) Moved RecursiveCrossProcessLock out of .mm file to a common _posix file.
*) Added static method to ImportantFileWriter that does blocking write on the current thread.
*) Dedicated RLZ thread gone, replaced back with shutdown-blocking worker pool.


Review URL: https://chromiumcodereview.appspot.com/11308196

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@170179 0039d316-1c4b-4281-b951-d872f2087c98
20 files changed