Add TestBrowserThreadBundle into RenderViewHostTestHarness. Kill some unnecessary real threads.

chrome/browser/download/download_target_determiner_unittest.cc

Index: chrome/browser/download/download_target_determiner_unittest.cc
diff --git a/chrome/browser/download/download_target_determiner_unittest.cc b/chrome/browser/download/download_target_determiner_unittest.cc
index debdbc687dc200cd92c0578c147d2b9afe98be8a..9d398d15af60ed579ebbf9b8016c1f7f72e2f711 100644
--- a/chrome/browser/download/download_target_determiner_unittest.cc
+++ b/chrome/browser/download/download_target_determiner_unittest.cc
@@ -178,9 +178,7 @@ class MockDownloadTargetDeterminerDelegate
 };
 
 class DownloadTargetDeterminerTest : public ChromeRenderViewHostTestHarness {
- public:
-  DownloadTargetDeterminerTest();
-
+ protected:
   // ::testing::Test
   virtual void SetUp() OVERRIDE;
   virtual void TearDown() OVERRIDE;
@@ -245,16 +243,8 @@ class DownloadTargetDeterminerTest : public ChromeRenderViewHostTestHarness {
   NullWebContentsDelegate web_contents_delegate_;
   base::ScopedTempDir test_download_dir_;
   base::FilePath test_virtual_dir_;
-  content::TestBrowserThread ui_thread_;
-  content::TestBrowserThread file_thread_;
 };
 
-DownloadTargetDeterminerTest::DownloadTargetDeterminerTest()
-    : ChromeRenderViewHostTestHarness(),
-      ui_thread_(content::BrowserThread::UI, &message_loop_),
-      file_thread_(content::BrowserThread::FILE, &message_loop_) {
-}
-
 void DownloadTargetDeterminerTest::SetUp() {
   ChromeRenderViewHostTestHarness::SetUp();
   CHECK(profile());
@@ -268,7 +258,6 @@ void DownloadTargetDeterminerTest::SetUp() {
 
 void DownloadTargetDeterminerTest::TearDown() {
   download_prefs_.reset();
-  message_loop_.RunUntilIdle();
   ChromeRenderViewHostTestHarness::TearDown();
 }