Reset global scoped task environment in http_stream_factory_impl_job_controller_unittest.cc

Reset the NetTestSuite's global task environment in unit test so the MOCK_TIME
environment doesn't leak into subsequent tests.

Bug: 791804
Change-Id: Ic5df1fc6c21c7ef6b88bff2d05a68b4636b7650a
Reviewed-on: https://chromium-review.googlesource.com/807287
Commit-Queue: Helen Li <xunjieli@chromium.org>
Reviewed-by: Zhongyi Shi <zhongyi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#521603}

net/http/http_stream_factory_impl_job_controller_unittest.cc

@@ -1507,6 +1507,11 @@ TEST_F(HttpStreamFactoryImplJobControllerTest, ResumeMainJobLaterCanceled) {
 
   EXPECT_TRUE(job_controller_->main_job());
   request_.reset();
+  // Reset task environment back to the default type.
+  // TODO(xunjieli): Remove this temporary workaround once crbug.com/791831 is
+  // fixed.
+  NetTestSuite::SetScopedTaskEnvironment(
+      base::test::ScopedTaskEnvironment::MainThreadType::IO);
 }
 
 // Test that main job is blocked for kMaxDelayTimeForMainJob(3s) if