[Signin][Android] Add histogram for duration of getting account ids

This CL adds Signin.AndroidGetAccountIdsTime histogram that tracks how
much time it takes to get account ids for all accounts on the device.

Bug: 906713
Change-Id: Ie59e815fcb469ced15fe308378e7c3fbc07d776a
Reviewed-on: https://chromium-review.googlesource.com/c/1342997
Commit-Queue: Boris Sazonov <bsazonov@chromium.org>
Reviewed-by: Jesse Doherty <jwd@chromium.org>
Reviewed-by: Mihai Sardarescu <msarda@chromium.org>
Cr-Commit-Position: refs/heads/master@{#610376}

chrome/android/java/src/org/chromium/chrome/browser/signin/AccountTrackerService.java

@@ -4,6 +4,7 @@
 
 package org.chromium.chrome.browser.signin;
 
+import android.os.SystemClock;
 import android.support.annotation.IntDef;
 
 import org.chromium.base.Log;
@@ -11,6 +12,7 @@ import org.chromium.base.ObserverList;
 import org.chromium.base.ThreadUtils;
 import org.chromium.base.VisibleForTesting;
 import org.chromium.base.annotations.JNINamespace;
+import org.chromium.base.metrics.RecordHistogram;
 import org.chromium.base.task.AsyncTask;
 import org.chromium.components.signin.AccountIdProvider;
 import org.chromium.components.signin.AccountManagerFacade;
@@ -18,6 +20,7 @@ import org.chromium.components.signin.AccountsChangeObserver;
 
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
+import java.util.concurrent.TimeUnit;
 
 /**
 * Android wrapper of AccountTrackerService which provides access from the java layer.
@@ -136,12 +139,20 @@ public class AccountTrackerService {
                 @Override
                 public String[][] doInBackground() {
                     Log.d(TAG, "Getting id/email mapping");
+
+                    long seedingStartTime = SystemClock.elapsedRealtime();
+
                     String[][] accountIdNameMap = new String[2][accounts.size()];
                     for (int i = 0; i < accounts.size(); ++i) {
                         accountIdNameMap[0][i] =
                                 accountIdProvider.getAccountId(accounts.get(i).name);
                         accountIdNameMap[1][i] = accounts.get(i).name;
                     }
+
+                    RecordHistogram.recordTimesHistogram("Signin.AndroidGetAccountIdsTime",
+                            SystemClock.elapsedRealtime() - seedingStartTime,
+                            TimeUnit.MILLISECONDS);
+
                     return accountIdNameMap;
                 }
                 @Override

tools/metrics/histograms/histograms.xml

@@ -102450,6 +102450,13 @@ uploading your change for review.
   </summary>
 </histogram>
 
+<histogram name="Signin.AndroidGetAccountIdsTime" units="ms">
+  <owner>bsazonov@chromium.org</owner>
+  <summary>
+    The time it takes to retrieve Gaia ids for all accounts from GoogleAuthUtil.
+  </summary>
+</histogram>
+
 <histogram name="Signin.AndroidGetAccountsTime" units="ms">
   <owner>nyquist@chromium.org</owner>
   <summary>