Use ScopedTaskEnvironment instead of MessageLoop in content unit tests.

content/browser/android/url_request_content_job_unittest.cc

Index: content/browser/android/url_request_content_job_unittest.cc
diff --git a/content/browser/android/url_request_content_job_unittest.cc b/content/browser/android/url_request_content_job_unittest.cc
index 8dcef62ec45b488208ae19811828bff1004b3259..2082aa9ce11c043ff1c19ddc222f326aaf24191f 100644
--- a/content/browser/android/url_request_content_job_unittest.cc
+++ b/content/browser/android/url_request_content_job_unittest.cc
@@ -12,6 +12,7 @@
 #include "base/files/file_util.h"
 #include "base/run_loop.h"
 #include "base/strings/stringprintf.h"
+#include "base/test/scoped_task_environment.h"
 #include "base/test/test_file_util.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "net/url_request/url_request.h"
@@ -116,7 +117,7 @@ class URLRequestContentJobTest : public testing::Test {
   // retrieved.
   void RunRequest(const Range* range);
 
-  base::MessageLoop message_loop_;
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
   JobObserverImpl observer_;
   net::TestURLRequestContext context_;
   net::TestDelegate delegate_;