Use QuitTask instead of Quit() to signal request completion.

Use QuitTask instead of Quit() to signal request completion.
This allows for cases where the request complete callback is invoked outside a message loop,
for e.g. in TestPostChunkedDataAfterStart(). Quit() can only be invoked inside a message
loop whereas posting a QuitTask to the message loop can be done from anywhere.

BUG=none
TEST=TestPostChunkedDataAfterStart passes through the tsan bots and net_unittests in general runs fine.

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=72493

[wtc, 2011-01-25 15:46:43]

LGTM.  Please use "svn blame" to find out who wrote the
code you modified, and ask him for a second review.  You
can check this in first, with the suggested change below.

http://codereview.chromium.org/6329019/diff/1/net/url_request/url_request_uni...
File net/url_request/url_request_unittest.h (right):

http://codereview.chromium.org/6329019/diff/1/net/url_request/url_request_uni...
net/url_request/url_request_unittest.h:226: MessageLoop::current()->Quit();
Please make the same change here for consistency.

[Satish, 2011-01-25 16:14:29]

Thanks, submitted.

> LGTM.  Please use "svn blame" to find out who wrote the
> code you modified, and ask him for a second review.  You
> can check this in first, with the suggested change below.

"git blame" shows that that code was part of the initial commit, so I presume we
don't have a real person's name associated with it?