Reenable GetStats test.

Also increasing start bitrate to have the test go significantly faster
on average. Hopefully an assert hit in the jitter buffer while running
this test was fixed in r7735.

R=stefan@webrtc.org
BUG=4014

Review URL: https://webrtc-codereview.appspot.com/26239004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@7744 4adac7df-926f-26a2-2b94-8c16560cd09d
Add back EXPECT_TRUEs.

These shouldn't fail, but EXPECT_TRUE gives nicer error messages that
work in Release. These changes got through unreviewed in r7726.

R=stefan@webrtc.org
BUG=

Review URL: https://webrtc-codereview.appspot.com/26249004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@7745 4adac7df-926f-26a2-2b94-8c16560cd09d