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.

Review URL: http://codereview.chromium.org/6329019

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@72493 0039d316-1c4b-4281-b951-d872f2087c98

net/url_request/url_request_unittest.h

@@ -223,7 +223,7 @@ class TestDelegate : public net::URLRequest::Delegate {
     received_redirect_count_++;
     if (quit_on_redirect_) {
       *defer_redirect = true;
-      MessageLoop::current()->Quit();
+      MessageLoop::current()->PostTask(FROM_HERE, new MessageLoop::QuitTask());
     } else if (cancel_in_rr_) {
       request->Cancel();
     }
@@ -290,7 +290,7 @@ class TestDelegate : public net::URLRequest::Delegate {
 
   virtual void OnResponseCompleted(net::URLRequest* request) {
     if (quit_on_complete_)
-      MessageLoop::current()->Quit();
+      MessageLoop::current()->PostTask(FROM_HERE, new MessageLoop::QuitTask());
   }
 
   void OnAuthRequired(net::URLRequest* request,