Fix crash when system retains an accessibility object.

This is a follow-up to r207709.

BUG=242944

Review URL: https://codereview.chromium.org/58993002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233506 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 233506
Removed SpdyProxyAuth.State histogram

The change to UMA aligns metrics for the data reduction proxy on
Android and iOS.

BUG=241518

Review URL: https://codereview.chromium.org/59113012

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233507 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 233507