Add TestBrowserThreadBundle into RenderViewHostTestHarness. Kill some unnecessary real threads.

content/content_tests.gypi

Index: content/content_tests.gypi
diff --git a/content/content_tests.gypi b/content/content_tests.gypi
index 0231411483515b2a65ecc7b57a1f611c82adcd6c..8f3662fe1ab56e9ea855bbff915279b84b221756 100644
--- a/content/content_tests.gypi
+++ b/content/content_tests.gypi
@@ -24,9 +24,9 @@
         '..',
       ],
       'sources': [
-        'public/test/browser_test.h',
         'public/test/browser_test_base.cc',
         'public/test/browser_test_base.h',
+        'public/test/browser_test.h',
         'public/test/browser_test_utils.cc',
         'public/test/browser_test_utils.h',
         'public/test/content_test_suite_base.cc',
@@ -57,6 +57,8 @@
         'public/test/render_widget_test.h',
         'public/test/test_browser_context.cc',
         'public/test/test_browser_context.h',
+        'public/test/test_browser_thread_bundle.cc',
+        'public/test/test_browser_thread_bundle.h',
         'public/test/test_browser_thread.cc',
         'public/test/test_browser_thread.h',
         'public/test/test_content_client_initializer.cc',