Android: UMA histogram for coldstart-to-commit

chrome/browser/android/tab_android.cc

Index: chrome/browser/android/tab_android.cc
diff --git a/chrome/browser/android/tab_android.cc b/chrome/browser/android/tab_android.cc
index 7354f24aac174ab3f381da39389d80b185b167c0..e7ce1c8d17890596a60fb6293005ec400bed861e 100644
--- a/chrome/browser/android/tab_android.cc
+++ b/chrome/browser/android/tab_android.cc
@@ -8,7 +8,9 @@
 #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"
@@ -748,3 +750,19 @@ static void Init(JNIEnv* env, jobject obj) {
 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);
+}