Switch content tests to use BrowserThreadImpl directly.

content/browser/download/base_file_unittest.cc

Index: content/browser/download/base_file_unittest.cc
diff --git a/content/browser/download/base_file_unittest.cc b/content/browser/download/base_file_unittest.cc
index ee518c3aedb181033d9b5cd4550a3d85dceb984d..e14b61874ba6a65ca40f2c787b51eeb7bbf197c7 100644
--- a/content/browser/download/base_file_unittest.cc
+++ b/content/browser/download/base_file_unittest.cc
@@ -10,12 +10,14 @@
 #include "base/scoped_temp_dir.h"
 #include "base/string_number_conversions.h"
 #include "base/test/test_file_util.h"
-#include "content/test/test_browser_thread.h"
+#include "content/browser/browser_thread_impl.h"
 #include "net/base/file_stream.h"
 #include "net/base/mock_file_stream.h"
 #include "net/base/net_errors.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
+using content::BrowserThreadImpl;
+
 namespace {
 
 const char kTestData1[] = "Let's write some data to the file!\n";
@@ -162,7 +164,7 @@ class BaseFileTest : public testing::Test {
 
   // Mock file thread to satisfy debug checks in BaseFile.
   MessageLoop message_loop_;
-  content::TestBrowserThread file_thread_;
+  BrowserThreadImpl file_thread_;
 };
 
 // Test the most basic scenario: just create the object and do a sanity check