Add a feature to use process start time for Android startup metrics

This allows using Process.getStartUptimeMillis() for startup metrics,
which will include the time spent loading java code.

Bug: 1126301
Change-Id: Ia5b050ba268b3445a7dd934fab409298ce9b3c32
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2399918Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Commit-Queue: Clark DuVall <cduvall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#805319}

base/android/java/src/org/chromium/base/compat/ApiHelperForN.java

@@ -14,6 +14,7 @@ import android.content.pm.PackageManager;
 import android.graphics.Bitmap;
 import android.media.MediaCodec.CryptoInfo;
 import android.os.Build;
+import android.os.Process;
 import android.security.NetworkSecurityPolicy;
 import android.view.MotionEvent;
 import android.view.PointerIcon;
@@ -85,4 +86,9 @@ public final class ApiHelperForN {
     public static PointerIcon onResolvePointerIcon(View view, MotionEvent event, int pointerIndex) {
         return view.onResolvePointerIcon(event, pointerIndex);
     }
+
+    /** See {@link Process#getStartUptimeMillis()}. */
+    public static long getStartUptimeMillis() {
+        return Process.getStartUptimeMillis();
+    }
 }

chrome/android/java/src/org/chromium/chrome/browser/metrics/UmaUtils.java

@@ -4,12 +4,14 @@
 
 package org.chromium.chrome.browser.metrics;
 
+import android.os.Build;
 import android.os.SystemClock;
 
 import org.chromium.base.annotations.CalledByNative;
 import org.chromium.base.annotations.JNINamespace;
 import org.chromium.base.annotations.MainDex;
 import org.chromium.base.annotations.NativeMethods;
+import org.chromium.base.compat.ApiHelperForN;
 
 /**
  * Utilities to support startup metrics - Android version.
@@ -87,7 +89,10 @@ public class UmaUtils {
     }
 
     @CalledByNative
-    public static long getApplicationStartTime() {
+    public static long getApplicationStartTime(boolean useProcessStartTime) {
+        if (useProcessStartTime && Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
+            return ApiHelperForN.getStartUptimeMillis();
+        }
         return sApplicationStartTimeMs;
     }
 

chrome/app/android/chrome_main_delegate_android.cc

@@ -24,8 +24,14 @@
 #include "components/safe_browsing/android/safe_browsing_api_handler_bridge.h"
 #endif
 
+namespace {
 using safe_browsing::SafeBrowsingApiHandler;
 
+// Whether to use the process start time for startup metrics.
+const base::Feature kUseProcessStartTimeForMetrics{
+    "UseProcessStartTimeForMetrics", base::FEATURE_DISABLED_BY_DEFAULT};
+}  // namespace
+
 // ChromeMainDelegateAndroid is created when the library is loaded. It is always
 // done in the process' main Java thread. But for a non-browser process, e.g.
 // renderer process, it is not the native Chrome's main thread.
@@ -87,7 +93,8 @@ int ChromeMainDelegateAndroid::RunProcess(
   // start time of the application, and will be same for all requests.
   if (!browser_runner_) {
     startup_metric_utils::RecordApplicationStartTime(
-        chrome::android::GetApplicationStartTime());
+        chrome::android::GetApplicationStartTime(
+            base::FeatureList::IsEnabled(kUseProcessStartTimeForMetrics)));
     browser_runner_ = content::BrowserMainRunner::Create();
   }
 

chrome/browser/android/metrics/uma_utils.cc

@@ -18,10 +18,10 @@ class PrefService;
 namespace chrome {
 namespace android {
 
-base::TimeTicks GetApplicationStartTime() {
+base::TimeTicks GetApplicationStartTime(bool use_process_start_time) {
   JNIEnv* env = base::android::AttachCurrentThread();
   return base::TimeTicks::FromUptimeMillis(
-      Java_UmaUtils_getApplicationStartTime(env));
+      Java_UmaUtils_getApplicationStartTime(env, use_process_start_time));
 }
 
 static jboolean JNI_UmaUtils_IsClientInMetricsReportingSample(JNIEnv* env) {

chrome/browser/android/metrics/uma_utils.h

@@ -12,7 +12,7 @@
 namespace chrome {
 namespace android {
 
-base::TimeTicks GetApplicationStartTime();
+base::TimeTicks GetApplicationStartTime(bool use_process_start_time);
 
 // Sets whether UMA reporting is enabled. This will call to Java to update
 // the shared preference that is the source of truth for UMA reporting.