Add AwVariationsSeedFetcher and refactory VariationsSeedFetcher

components/variations/android/java/src/org/chromium/components/variations/firstrun/VariationsSeedFetcher.java

 // Copyright 2015 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.components.variations.firstrun;
 
-import android.content.Context;
 import android.content.SharedPreferences;
 import android.os.SystemClock;
 
 import org.chromium.base.ContextUtils;
 import org.chromium.base.Log;
 import org.chromium.base.ThreadUtils;
 import org.chromium.base.VisibleForTesting;
 import org.chromium.base.metrics.CachedMetrics.SparseHistogramSample;
 import org.chromium.base.metrics.CachedMetrics.TimesHistogramSample;
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.net.HttpURLConnection;
 import java.net.MalformedURLException;
 import java.net.SocketTimeoutException;
 import java.net.URL;
 import java.net.UnknownHostException;
+import java.util.HashMap;
+import java.util.Map;
 import java.util.concurrent.TimeUnit;
 
 /**
  * Fetches the variations seed before the actual first run of Chrome.
  */
 public class VariationsSeedFetcher {
     private static final String TAG = "VariationsSeedFetch";
-    private static final String VARIATIONS_SERVER_URL =
-            "https://clientservices.googleapis.com/chrome-variations/seed?osname=android";
+
+    public static final String VARIATIONS_PLATFORM = "android";

[Alexei Svitkine (slow), 2017/07/06 22:01:10]

Nit: VARIATIONS_PLATFORM_ANDROID

Also, add a blank line below it.

+    public static final String VARIATIONS_SERVER_URL =
+            "https://clientservices.googleapis.com/chrome-variations/seed?osname=";
+
+    public static final String SIGNATURE_HEADERFIELD = "X-Seed-Signature";
+    public static final String COUNTRY_HEADERFIELD = "X-Country";
+    public static final String DATE_HEADERFIELD = "Date";
+    public static final String IM_HEADERFIELD = "IM";
 
     private static final int BUFFER_SIZE = 4096;
     private static final int READ_TIMEOUT = 3000; // time in ms
     private static final int REQUEST_TIMEOUT = 1000; // time in ms
 
     // Values for the "Variations.FirstRun.SeedFetchResult" sparse histogram, which also logs
     // HTTP result codes. These are negative so that they don't conflict with the HTTP codes.
     // These values should not be renumbered or re-used since they are logged to UMA.
     private static final int SEED_FETCH_RESULT_UNKNOWN_HOST_EXCEPTION = -3;
     private static final int SEED_FETCH_RESULT_TIMEOUT = -2;
@@ skipping 25 matching lines @@
      * Override the VariationsSeedFetcher, typically with a mock, for testing classes that depend on
      * this one.
      * @param fetcher the mock.
      */
     @VisibleForTesting
     public static void setVariationsSeedFetcherForTesting(VariationsSeedFetcher fetcher) {
         sInstance = fetcher;
     }
 
     @VisibleForTesting
-    protected HttpURLConnection getServerConnection(String restrictMode)
+    protected HttpURLConnection getServerConnection(String urlString, String restrictMode)
             throws MalformedURLException, IOException {
-        String urlString = VARIATIONS_SERVER_URL;
         if (restrictMode != null && !restrictMode.isEmpty()) {
             urlString += "&restrict=" + restrictMode;
         }
         URL url = new URL(urlString);
         return (HttpURLConnection) url.openConnection();
     }
 
     /**
      * Fetch the first run variations seed.
      * @param restrictMode The restrict mode parameter to pass to the server via a URL param.
      */
     public void fetchSeed(String restrictMode) {
         assert !ThreadUtils.runningOnUiThread();
         // Prevent multiple simultaneous fetches
         synchronized (sLock) {
-            Context context = ContextUtils.getApplicationContext();
             SharedPreferences prefs = ContextUtils.getAppSharedPreferences();
             // Early return if an attempt has already been made to fetch the seed, even if it
             // failed. Only attempt to get the initial Java seed once, since a failure probably
             // indicates a network problem that is unlikely to be resolved by a second attempt.
             // Note that VariationsSeedBridge.hasNativePref() is a pure Java function, reading an
             // Android preference that is set when the seed is fetched by the native code.
             if (prefs.getBoolean(VARIATIONS_INITIALIZED_PREF, false)
                     || VariationsSeedBridge.hasNativePref()) {
                 return;
             }
-            downloadContent(context, restrictMode);
+
+            Map<String, String> headerFields = new HashMap<String, String>();
+            byte[] rawSeed = downloadContent(
+                    VARIATIONS_SERVER_URL + VARIATIONS_PLATFORM, restrictMode, headerFields);
+            if (rawSeed != null) {
+                String signature = headerFields.get(SIGNATURE_HEADERFIELD);
+                String country = headerFields.get(COUNTRY_HEADERFIELD);
+                String date = headerFields.get(DATE_HEADERFIELD);
+                boolean isGzipCompressed = headerFields.get(IM_HEADERFIELD).equals("gzip");
+                VariationsSeedBridge.setVariationsFirstRunSeed(
+                        rawSeed, signature, country, date, isGzipCompressed);
+            }
             prefs.edit().putBoolean(VARIATIONS_INITIALIZED_PREF, true).apply();
         }
     }
 
     private void recordFetchResultOrCode(int resultOrCode) {
         SparseHistogramSample histogram =
                 new SparseHistogramSample("Variations.FirstRun.SeedFetchResult");
         histogram.record(resultOrCode);
     }
 
     private void recordSeedFetchTime(long timeDeltaMillis) {
         Log.i(TAG, "Fetched first run seed in " + timeDeltaMillis + " ms");
         TimesHistogramSample histogram = new TimesHistogramSample(
                 "Variations.FirstRun.SeedFetchTime", TimeUnit.MILLISECONDS);
         histogram.record(timeDeltaMillis);
     }
 
     private void recordSeedConnectTime(long timeDeltaMillis) {
         TimesHistogramSample histogram = new TimesHistogramSample(
                 "Variations.FirstRun.SeedConnectTime", TimeUnit.MILLISECONDS);
         histogram.record(timeDeltaMillis);
     }
 
-    private void downloadContent(Context context, String restrictMode) {
+    public byte[] downloadContent(
+            String urlString, String restrictMode, Map<String, String> headFields) {
         HttpURLConnection connection = null;
+        byte[] rawSeed = null;
         try {
             long startTimeMillis = SystemClock.elapsedRealtime();
-            connection = getServerConnection(restrictMode);
+            connection = getServerConnection(urlString, restrictMode);
             connection.setReadTimeout(READ_TIMEOUT);
             connection.setConnectTimeout(REQUEST_TIMEOUT);
             connection.setDoInput(true);
             connection.setRequestProperty("A-IM", "gzip");
             connection.connect();
             int responseCode = connection.getResponseCode();
             recordFetchResultOrCode(responseCode);
             if (responseCode != HttpURLConnection.HTTP_OK) {
                 Log.w(TAG, "Non-OK response code = %d", responseCode);
-                return;
+                return null;
             }
 
             recordSeedConnectTime(SystemClock.elapsedRealtime() - startTimeMillis);
             // Convert the InputStream into a byte array.
-            byte[] rawSeed = getRawSeed(connection);
-            String signature = getHeaderFieldOrEmpty(connection, "X-Seed-Signature");
-            String country = getHeaderFieldOrEmpty(connection, "X-Country");
-            String date = getHeaderFieldOrEmpty(connection, "Date");
-            boolean isGzipCompressed = getHeaderFieldOrEmpty(connection, "IM").equals("gzip");
-            VariationsSeedBridge.setVariationsFirstRunSeed(
-                    rawSeed, signature, country, date, isGzipCompressed);
+            rawSeed = getRawSeed(connection);
+            headFields.put(SIGNATURE_HEADERFIELD,
+                    getHeaderFieldOrEmpty(connection, SIGNATURE_HEADERFIELD));
+            headFields.put(
+                    COUNTRY_HEADERFIELD, getHeaderFieldOrEmpty(connection, COUNTRY_HEADERFIELD));
+            headFields.put(DATE_HEADERFIELD, getHeaderFieldOrEmpty(connection, DATE_HEADERFIELD));
+            headFields.put(IM_HEADERFIELD, getHeaderFieldOrEmpty(connection, IM_HEADERFIELD));

[Alexei Svitkine (slow), 2017/07/06 22:01:10]

Suggest defining a simple class with these fields + the seed bytes instead of
using a map out-parameter.

Then, it could still be a simple return value without any map params and you
don't need the constants for the header names - keep them inline here in one
place.

             recordSeedFetchTime(SystemClock.elapsedRealtime() - startTimeMillis);
         } catch (SocketTimeoutException e) {
             recordFetchResultOrCode(SEED_FETCH_RESULT_TIMEOUT);
             Log.w(TAG, "SocketTimeoutException fetching first run seed: ", e);
         } catch (UnknownHostException e) {
             recordFetchResultOrCode(SEED_FETCH_RESULT_UNKNOWN_HOST_EXCEPTION);
             Log.w(TAG, "UnknownHostException fetching first run seed: ", e);
         } catch (IOException e) {
             recordFetchResultOrCode(SEED_FETCH_RESULT_IOEXCEPTION);
             Log.w(TAG, "IOException fetching first run seed: ", e);
         } finally {
             if (connection != null) {
                 connection.disconnect();
             }
         }
+        return rawSeed;

[paulmiller, 2017/07/06 23:09:05]

It looks like this can be null, but AwVariationsSeedFetcher assumes it's not
null. Since it's not obvious from the method name that it might return null, a
safer design might be to propagate the exception rather than returning null.
Then change AwVariationsSeedFetcher to handle the exception.

     }
 
     private String getHeaderFieldOrEmpty(HttpURLConnection connection, String name) {
         String headerField = connection.getHeaderField(name);
         if (headerField == null) {
             return "";
         }
         return headerField.trim();
     }
 
@@ skipping 12 matching lines @@
     private byte[] convertInputStreamToByteArray(InputStream inputStream) throws IOException {
         ByteArrayOutputStream byteBuffer = new ByteArrayOutputStream();
         byte[] buffer = new byte[BUFFER_SIZE];
         int charactersReadCount = 0;
         while ((charactersReadCount = inputStream.read(buffer)) != -1) {
             byteBuffer.write(buffer, 0, charactersReadCount);
         }
         return byteBuffer.toByteArray();
     }
 }