When clearing plugin data at shutdown, wait for it to finish.

Also, Add some browser tests for clearing plugin data and enable npapi_test_plugin on 64-bit Linux; apparently it's been fixed.

BUG=58235, 18337, 26625
TEST=PluginDataRemoverTest.*

Review URL: http://codereview.chromium.org/6308001

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@72123 0039d316-1c4b-4281-b951-d872f2087c98
10 files changed