Remove net-internals page for throttling, introduce flag for extension devs instead.

net/url_request/url_request_throttler_manager.cc

Index: net/url_request/url_request_throttler_manager.cc
diff --git a/net/url_request/url_request_throttler_manager.cc b/net/url_request/url_request_throttler_manager.cc
index e29f5c259be31497b998747a2cd61e892c3870d1..048cc32cd228588b358ac397de60577718bc92e4 100644
--- a/net/url_request/url_request_throttler_manager.cc
+++ b/net/url_request/url_request_throttler_manager.cc
@@ -149,10 +149,9 @@ void URLRequestThrottlerManager::OnOnlineStateChanged(bool online) {
   OnNetworkChange();
 }
 
-// TODO(joi): Turn throttling on by default when appropriate.
 URLRequestThrottlerManager::URLRequestThrottlerManager()
     : requests_since_last_gc_(0),
-      enforce_throttling_(false),
+      enforce_throttling_(true),
       enable_thread_checks_(false),
       logged_for_localhost_disabled_(false),
       registered_from_thread_(base::kInvalidThreadId) {