Decreasing WebRTC manual test timeout 300->180 secs.
Decreasing WebRTC manual test timeout 300->180 secs.

The video qualtiy test generally takes about 90 seconds to execute on
the bots, so a 300 second timeout seemed like overkill. This is
especially so now that all tests happen to be failing, which makes the
browser test target take 48 minutes to execute (crbug.com/281268)

BUG=281268

Review URL: https://codereview.chromium.org/94353002

git-svn-id: 239fca9b83025a0b6f823aeeca02ba5be3d9fd76@238335 0039d316-1c4b-4281-b951-d872f2087c98

eunchong/build,eunchong/build,eunchong/build,eunchong/build