Android: UMA histogram for coldstart-to-commit

chrome/browser/android/tab_android.cc

 // Copyright (c) 2012 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/android/tab_android.h"
 
 #include "base/android/jni_android.h"
 #include "base/android/jni_array.h"
 #include "base/android/jni_string.h"
 #include "base/debug/trace_event.h"
+#include "base/metrics/histogram.h"
 #include "chrome/browser/android/chrome_web_contents_delegate_android.h"
+#include "chrome/browser/android/uma_utils.h"
 #include "chrome/browser/browser_about_handler.h"
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/content_settings/tab_specific_content_settings.h"
 #include "chrome/browser/favicon/favicon_tab_helper.h"
 #include "chrome/browser/infobars/infobar_service.h"
 #include "chrome/browser/prerender/prerender_contents.h"
 #include "chrome/browser/prerender/prerender_manager.h"
 #include "chrome/browser/prerender/prerender_manager_factory.h"
 #include "chrome/browser/printing/print_view_manager_basic.h"
 #include "chrome/browser/profiles/profile.h"
@@ skipping 719 matching lines @@
 static void Init(JNIEnv* env, jobject obj) {
   TRACE_EVENT0("native", "TabAndroid::Init");
   // This will automatically bind to the Java object and pass ownership there.
   new TabAndroid(env, obj);
 }
 
 // static
 bool TabAndroid::RegisterTabAndroid(JNIEnv* env) {
   return RegisterNativesImpl(env);
 }
+
+static void RecordStartupToCommitUma(JNIEnv* env, jclass jcaller) {
+  // Currently it takes about 2000ms to commit a navigation if the measurement
+  // begins very early in the browser start. How many buckets (b) are needed to
+  // explore the _typical_ values with granularity 100ms and a maximum duration
+  // of 1 minute?
+  //   s^{n+1} / s^{n} = 2100 / 2000
+  //   s = 1.05
+  //   s^b = 60000
+  //   b = ln(60000) / ln(1.05) ~= 225
+  UMA_HISTOGRAM_CUSTOM_TIMES("Startup.FirstCommitNavigationTime",
+      base::Time::Now() - chrome::android::GetMainEntryPointTime(),
+      base::TimeDelta::FromMilliseconds(1),
+      base::TimeDelta::FromMinutes(1),
+      225);
+}