Implement A/B experiment for anti-DDoS.

chrome/browser/ui/webui/net_internals_ui.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/ui/webui/net_internals_ui.h"
 
 #include <algorithm>
 #include <list>
 #include <string>
 #include <utility>
 #include <vector>
 
 #include "base/base64.h"
 #include "base/command_line.h"
 #include "base/memory/singleton.h"
 #include "base/message_loop.h"
+#include "base/metrics/field_trial.h"  // TODO(joi): Remove after the trial ends.
 #include "base/path_service.h"
 #include "base/string_number_conversions.h"
 #include "base/string_piece.h"
 #include "base/string_split.h"
 #include "base/string_util.h"
 #include "base/utf_string_conversions.h"
 #include "base/values.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/io_thread.h"
 #include "chrome/browser/net/chrome_net_log.h"
@@ skipping 208 matching lines @@
     CancelableRequestConsumer consumer_;
     // Libcros request handle.
     CancelableRequestProvider::Handle syslogs_request_id_;
   };
 #endif
 
   // The pref member about whether HTTP throttling is enabled, which needs to
   // be accessed on the UI thread.
   BooleanPrefMember http_throttling_enabled_;
 
+  // The pref member that determines whether experimentation on HTTP throttling
+  // is allowed (this becomes false once the user explicitly sets the
+  // feature to on or off).
+  BooleanPrefMember http_throttling_may_experiment_;
+
   // OnRendererReady invokes this callback to do the part of message handling
   // that needs to happen on the IO thread.
   scoped_ptr<WebUI::MessageCallback> renderer_ready_io_callback_;
 
   // This is the "real" message handler, which lives on the IO thread.
   scoped_refptr<IOThreadImpl> proxy_;
 
   base::WeakPtr<prerender::PrerenderManager> prerender_manager_;
 
 #ifdef OS_CHROMEOS
@@ skipping 250 matching lines @@
     // Notify the handler on the IO thread that the renderer is gone.
     BrowserThread::PostTask(BrowserThread::IO, FROM_HERE,
         NewRunnableMethod(proxy_.get(), &IOThreadImpl::Detach));
   }
 }
 
 WebUIMessageHandler* NetInternalsMessageHandler::Attach(WebUI* web_ui) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
   PrefService* pref_service = web_ui->GetProfile()->GetPrefs();
-  http_throttling_enabled_.Init(prefs::kHttpThrottlingEnabled, pref_service,
-                                this);
+  http_throttling_enabled_.Init(
+      prefs::kHttpThrottlingEnabled, pref_service, this);
+  http_throttling_may_experiment_.Init(
+      prefs::kHttpThrottlingMayExperiment, pref_service, NULL);
 
   proxy_ = new IOThreadImpl(this->AsWeakPtr(), g_browser_process->io_thread(),
                             web_ui->GetProfile()->GetRequestContext());
 #ifdef OS_CHROMEOS
   syslogs_getter_.reset(new SystemLogsGetter(this,
       chromeos::SystemAccess::GetInstance()));
 #endif
   renderer_ready_io_callback_.reset(
       proxy_->CreateCallback(&IOThreadImpl::OnRendererReady));
 
@@ skipping 133 matching lines @@
 void NetInternalsMessageHandler::OnEnableHttpThrottling(const ListValue* list) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
   bool enable = false;
   if (!list->GetBoolean(0, &enable)) {
     NOTREACHED();
     return;
   }
 
   http_throttling_enabled_.SetValue(enable);
+
+  // We never receive OnEnableHttpThrottling unless the user has modified
+  // the value of the checkbox on the about:net-internals page.  Once the
+  // user does that, we no longer allow experiments to control its value.
+  if (http_throttling_may_experiment_.GetValue()) {
+    http_throttling_may_experiment_.SetValue(false);
+
+    // Disable the ongoing trial so that histograms after this point
+    // show as being in the "Default" group of the trial.
+    base::FieldTrial* trial = base::FieldTrialList::Find(
+        "HttpThrottlingEnabled");
+    if (trial)
+      trial->Disable();
+  }
 }
 
 void NetInternalsMessageHandler::OnGetPrerenderInfo(const ListValue* list) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
   Value* value = NULL;
   prerender::PrerenderManager* prerender_manager = prerender_manager_.get();
   if (!prerender_manager) {
     value = new ListValue();
   } else {
@@ skipping 896 matching lines @@
 ////////////////////////////////////////////////////////////////////////////////
 
 NetInternalsUI::NetInternalsUI(TabContents* contents) : ChromeWebUI(contents) {
   AddMessageHandler((new NetInternalsMessageHandler())->Attach(this));
 
   NetInternalsHTMLSource* html_source = new NetInternalsHTMLSource();
 
   // Set up the chrome://net-internals/ source.
   GetProfile()->GetChromeURLDataManager()->AddDataSource(html_source);
 }