Move GeolocationClientMock to modules. Use internals instead of TestRunner.

This is part of the effort to remove dependencies from core to modules.
Next step is to remove the old code from TestRunner and delete 
WebGeolocationClientMock and its friends.

BUG=336263

Review URL: https://codereview.chromium.org/141163008

git-svn-id: svn://svn.chromium.org/blink/trunk@165572 bbb929c8-8fbe-4397-9dbb-9b2b20218538