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

chrome/browser/io_thread.cc

Index: chrome/browser/io_thread.cc
diff --git a/chrome/browser/io_thread.cc b/chrome/browser/io_thread.cc
index 4bdc0aa784d88970b713ab4a64e544c4f695963d..3754e2b3d1bad60d6964ab4bee3e84f537e5fa08 100644
--- a/chrome/browser/io_thread.cc
+++ b/chrome/browser/io_thread.cc
@@ -32,6 +32,7 @@
 #include "chrome/browser/prefs/pref_service.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/common/pref_names.h"
+#include "chrome/common/url_constants.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/common/content_client.h"
 #include "content/public/common/url_fetcher.h"
@@ -53,6 +54,7 @@
 #include "net/proxy/proxy_config_service.h"
 #include "net/proxy/proxy_script_fetcher_impl.h"
 #include "net/proxy/proxy_service.h"
+#include "net/url_request/url_request.h"
 #include "net/url_request/url_request_throttler_manager.h"
 
 #if defined(USE_NSS)
@@ -72,6 +74,28 @@ class SafeBrowsingURLRequestContext;
 
 namespace {
 
+// Makes it so that the URLRequestThrottlerManager may only reject
+// requests that originate from extensions.
+class ChromeURLRequestThrottlerManagerDelegate
+    : public net::URLRequestThrottlerManagerDelegate {
+ public:
+  explicit ChromeURLRequestThrottlerManagerDelegate(bool enforce)
+      : enforce_(enforce) {
+  }
+
+  virtual bool MayRejectRequest(net::URLRequest* request) OVERRIDE {
+    if (enforce_) {
+      return request->first_party_for_cookies().scheme() !=
+          chrome::kExtensionScheme;
+    } else {
+      return false;
+    }
+  }
+
+ private:
+  bool enforce_;
+};
+
 // Custom URLRequestContext used by requests which aren't associated with a
 // particular profile. We need to use a subclass of URLRequestContext in order
 // to provide the correct User-Agent.
@@ -446,13 +470,15 @@ void IOThread::Init() {
   globals_->proxy_script_fetcher_ftp_transaction_factory.reset(
       new net::FtpNetworkLayer(globals_->host_resolver.get()));
 
-  globals_->throttler_manager.reset(new net::URLRequestThrottlerManager());
+  bool enforce_throttling = CommandLine::ForCurrentProcess()->HasSwitch(
+      switches::kDisableExtensionsHttpThrottling);
+  globals_->throttler_manager_delegate.reset(
+      new ChromeURLRequestThrottlerManagerDelegate(enforce_throttling));
+
+  globals_->throttler_manager.reset(new net::URLRequestThrottlerManager(
+      globals_->throttler_manager_delegate.get()));
   // Always done in production, disabled only for unit tests.
   globals_->throttler_manager->set_enable_thread_checks(true);
-  if (CommandLine::ForCurrentProcess()->HasSwitch(
-          switches::kDisableExtensionsHttpThrottling)) {
-    globals_->throttler_manager->set_enforce_throttling(false);
-  }
   globals_->throttler_manager->set_net_log(net_log_);
 
   globals_->proxy_script_fetcher_context.reset(