Add PartnerBookmark.LoadingTime

Record time spent on reading partner bookmarks, since this is part of
the critical path of showing bookmark UI.

Bug: 787132
Change-Id: I8aa68436b0d762d644691992bde0e2df095259f0
Reviewed-on: https://chromium-review.googlesource.com/825004Reviewed-by: Steven Holte <holte@chromium.org>
Reviewed-by: Theresa <twellington@chromium.org>
Commit-Queue: Wei-Yin Chen (陳威尹) <wychen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#524601}

chrome/android/java/src/org/chromium/chrome/browser/bookmarks/BookmarkBridge.java

@@ -4,6 +4,7 @@
 
 package org.chromium.chrome.browser.bookmarks;
 
+import android.os.SystemClock;
 import android.text.TextUtils;
 import android.util.Pair;
 
@@ -11,6 +12,7 @@ import org.chromium.base.ContextUtils;
 import org.chromium.base.ObserverList;
 import org.chromium.base.VisibleForTesting;
 import org.chromium.base.annotations.CalledByNative;
+import org.chromium.base.metrics.RecordHistogram;
 import org.chromium.chrome.browser.partnerbookmarks.PartnerBookmarksShim;
 import org.chromium.chrome.browser.profiles.Profile;
 import org.chromium.components.bookmarks.BookmarkId;
@@ -19,6 +21,7 @@ import org.chromium.components.url_formatter.UrlFormatter;
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.concurrent.TimeUnit;
 
 /**
  * Provides the communication channel for Android to fetch and manipulate the
@@ -303,10 +306,13 @@ public class BookmarkBridge {
             return true;
         }
 
+        long startTime = SystemClock.elapsedRealtime();
         addObserver(new BookmarkModelObserver() {
             @Override
             public void bookmarkModelLoaded() {
                 removeObserver(this);
+                RecordHistogram.recordTimesHistogram("PartnerBookmark.LoadingTime",
+                        SystemClock.elapsedRealtime() - startTime, TimeUnit.MILLISECONDS);
                 runAfterModelLoaded.run();
             }
             @Override

tools/metrics/histograms/histograms.xml

@@ -58879,6 +58879,14 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="PartnerBookmark.LoadingTime" units="ms">
+  <owner>wychen@chromium.org</owner>
+  <summary>
+    The time spent on loading partner bookmarks, from kickOffReading() to
+    bookmarkModelLoaded() callback.
+  </summary>
+</histogram>
+
 <histogram name="PartnerBookmark.Null" enum="BooleanNull">
   <owner>wychen@chromium.org</owner>
   <summary>