Photo Picker dialog: Add UMA statistics.

chrome/android/java/src/org/chromium/chrome/browser/photo_picker/BitmapScalerTask.java

 // Copyright 2017 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.
 
 package org.chromium.chrome.browser.photo_picker;
 
 import android.graphics.Bitmap;
 import android.os.AsyncTask;
+import android.os.SystemClock;
 import android.util.LruCache;
 
 import org.chromium.base.ThreadUtils;
+import org.chromium.base.metrics.RecordHistogram;
+
+import java.util.concurrent.TimeUnit;
 
 /**
  * A worker task to scale bitmaps in the background.
  */
 class BitmapScalerTask extends AsyncTask<Bitmap, Void, Bitmap> {
     private final LruCache<String, Bitmap> mCache;
     private final String mFilePath;
     private final int mSize;
 
     /**
      * A BitmapScalerTask constructor.
      */
     public BitmapScalerTask(LruCache<String, Bitmap> cache, String filePath, int size) {
         mCache = cache;
         mFilePath = filePath;
         mSize = size;
     }
 
     /**
      * Scales the image provided. Called on a non-UI thread.
      * @param params Ignored, do not use.
      * @return A sorted list of images (by last-modified first).
      */
     @Override
     protected Bitmap doInBackground(Bitmap... bitmaps) {
         assert !ThreadUtils.runningOnUiThread();
 
         if (isCancelled()) return null;
 
-        return BitmapUtils.scale(bitmaps[0], mSize, false);
+        long begin = SystemClock.elapsedRealtime();
+        Bitmap bitmap = BitmapUtils.scale(bitmaps[0], mSize, false);
+        long scaleTime = SystemClock.elapsedRealtime() - begin;
+        RecordHistogram.recordTimesHistogram(
+                "Android.PhotoPicker.BitmapScalerTask", scaleTime, TimeUnit.MILLISECONDS);
+        return bitmap;
     }
 
     /**
      * Communicates the results back to the client. Called on the UI thread.
      * @param result The resulting scaled bitmap.
      */
     @Override
     protected void onPostExecute(Bitmap result) {
         if (isCancelled()) {
             return;
         }
 
         mCache.put(mFilePath, result);
     }
 }