FakeVCD refactoring, moving some variable use into inner
thread.

Move manipulation of |capture_format_|, |fake_frame_| 
to be used only in the |capture_thread_| -- this is a
cleanup so that the behaviour is similar to other VCD
implementations where the "capture thread" does the 
heavy lifting and the other thread (whatever its name)
is mostly passing by messages and starting/stopping 
the "capture thread" (see f.i. Linux impl [1]). 

Following this cleanup, |client_| manipulation is 
shifted to the "capture_thread" as well.

|state_| disappears, substituted by checking of
|capture_thread_| running state.

[1] https://code.google.com/p/chromium/codesearch#chromium/src/media/video/capture/linux/video_capture_device_linux.cc&sq=package:chromium&type=cs&l=296

BUG=323893

Review URL: https://codereview.chromium.org/91523002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238677 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 238677