system_request_context() has to be called on the UI thread.
system_request_context() has to be called on the UI thread.

BUG=120714
TEST=Do an official build with dchecks enabled. Observe no dcheck 20s after startup.

Review URL: http://codereview.chromium.org/9877017

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@129563 0039d316-1c4b-4281-b951-d872f2087c98

gavinp/chromium,yitian134/chromium,yitian134/chromium,ropik/chromium,gavinp/chromium,ropik/chromium,yitian134/chromium,gavinp/chromium,ropik/chromium,adobe/chromium,gavinp/chromium,yitian134/chromium,adobe/chromium,adobe/chromium,adobe/chromium,yitian134/chromium,gavinp/chromium,ropik/chromium,yitian134/chromium,ropik/chromium,gavinp/chromium,adobe/chromium,adobe/chromium,adobe/chromium,yitian134/chromium,adobe/chromium,gavinp/chromium,yitian134/chromium,ropik/chromium,ropik/chromium,gavinp/chromium,gavinp/chromium,gavinp/chromium,yitian134/chromium,adobe/chromium,adobe/chromium,ropik/chromium,adobe/chromium,yitian134/chromium,ropik/chromium