Add UMA histograms to track very brief or frequent tabs and JS dialogs.

components/app_modal/javascript_dialog_manager.cc

 // Copyright 2014 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 "components/app_modal/javascript_dialog_manager.h"
 
 #include <utility>
 
 #include "base/bind.h"
 #include "base/i18n/rtl.h"
 #include "base/macros.h"
+#include "base/metrics/histogram_macros.h"
 #include "base/strings/utf_string_conversions.h"
 #include "components/app_modal/app_modal_dialog.h"
 #include "components/app_modal/app_modal_dialog_queue.h"
 #include "components/app_modal/javascript_app_modal_dialog.h"
 #include "components/app_modal/javascript_dialog_extensions_client.h"
 #include "components/app_modal/javascript_native_dialog_factory.h"
 #include "components/app_modal/native_app_modal_dialog.h"
 #include "components/url_formatter/elide_url.h"
 #include "content/public/browser/web_contents.h"
 #include "content/public/common/javascript_message_type.h"
@@ skipping 71 matching lines @@
   ChromeJavaScriptDialogExtraData* extra_data =
       &javascript_dialog_extra_data_
           [JavaScriptAppModalDialog::GetSerializedOriginForWebContents(
               web_contents)];
 
   if (extra_data->suppress_javascript_messages_) {
     *did_suppress_message = true;
     return;
   }
 
+  base::TimeTicks now = base::TimeTicks::Now();
+  if (!last_creation_time_.is_null()) {
+    // A new dialog has been created: log the time since the last one was
+    // created.
+    UMA_HISTOGRAM_MEDIUM_TIMES(
+        "JSDialogs.FineTiming.TimeBetweenDialogCreatedAndNextDialogCreated",
+        now - last_creation_time_);
+  }
+  last_creation_time_ = now;
+
+  // Also log the time since a dialog was closed, but only if this is the first
+  // dialog that was opened since the closing.
+  if (!last_close_time_.is_null()) {
+    UMA_HISTOGRAM_MEDIUM_TIMES(
+        "JSDialogs.FineTiming.TimeBetweenDialogClosedAndNextDialogCreated",
+        now - last_close_time_);
+    last_close_time_ = base::TimeTicks();
+  }
+
   bool is_alert = message_type == content::JAVASCRIPT_MESSAGE_TYPE_ALERT;
   base::string16 dialog_title =
       GetTitle(web_contents, origin_url, accept_lang, is_alert);
 
   extensions_client_->OnDialogOpened(web_contents);
 
   AppModalDialogQueue::GetInstance()->AddDialog(new JavaScriptAppModalDialog(
       web_contents,
       &javascript_dialog_extra_data_,
       dialog_title,
@@ skipping 129 matching lines @@
 void JavaScriptDialogManager::OnDialogClosed(
     content::WebContents* web_contents,
     DialogClosedCallback callback,
     bool success,
     const base::string16& user_input) {
   // If an extension opened this dialog then the extension may shut down its
   // lazy background page after the dialog closes. (Dialogs are closed before
   // their WebContents is destroyed so |web_contents| is still valid here.)
   extensions_client_->OnDialogClosed(web_contents);
 
+  last_close_time_ = base::TimeTicks::Now();
+
   callback.Run(success, user_input);
 }
 
 }  // namespace app_modal