Introduce a delegate to avoid hardcoding "chrome-extension" in net/.

content/common/net/url_fetcher_impl_unittest.cc

Index: content/common/net/url_fetcher_impl_unittest.cc
diff --git a/content/common/net/url_fetcher_impl_unittest.cc b/content/common/net/url_fetcher_impl_unittest.cc
index d8bacd0cbdad3704c635326312893344c4bb75eb..788bc9b415a6ac84a716aafe15edf08b51e59404 100644
--- a/content/common/net/url_fetcher_impl_unittest.cc
+++ b/content/common/net/url_fetcher_impl_unittest.cc
@@ -38,13 +38,16 @@ const char kTestServerFilePrefix[] = "files/";
 
 class ThrottlingTestURLRequestContext : public TestURLRequestContext {
  public:
-  ThrottlingTestURLRequestContext() : TestURLRequestContext(true) {
+  ThrottlingTestURLRequestContext()
+      : TestURLRequestContext(true),
+        throttler_manager_(&delegate_) {
     set_throttler_manager(&throttler_manager_);
     Init();
     DCHECK(throttler_manager() != NULL);
   }
 
  private:
+  TestURLRequestThrottlerManagerDelegate delegate_;
   net::URLRequestThrottlerManager throttler_manager_;
 };