Add AwVariationsSeedFetchService 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.concurrent.TimeUnit;
 
 /**
  * Fetches the variations seed before the actual first run of Chrome.
  */
 public class VariationsSeedFetcher {
     private static final String TAG = "VariationsSeedFetch";
+
+    public enum VariationsPlatform { ANDROID, ANDROID_WEBVIEW }
+
     private static final String VARIATIONS_SERVER_URL =
-            "https://clientservices.googleapis.com/chrome-variations/seed?osname=android";
+            "https://clientservices.googleapis.com/chrome-variations/seed?osname=";
 
     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;
     private static final int SEED_FETCH_RESULT_IOEXCEPTION = -1;
 
     @VisibleForTesting
     static final String VARIATIONS_INITIALIZED_PREF = "variations_initialized";
 
-    // Synchronization lock
+    // Synchronization lock to make singleton thread-safe
     private static final Object sLock = new Object();
 
     private static VariationsSeedFetcher sInstance;
 
     @VisibleForTesting
     VariationsSeedFetcher() {}
 
     public static VariationsSeedFetcher get() {
         // TODO(aberent) Check not running on UI thread. Doing so however makes Robolectric testing
         // of dependent classes difficult.
         synchronized (sLock) {
             if (sInstance == null) {
                 sInstance = new VariationsSeedFetcher();
             }
             return sInstance;
         }
     }
 
     /**
      * 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)
-            throws MalformedURLException, IOException {
+    protected HttpURLConnection getServerConnection(final VariationsPlatform platform,
+            final String restrictMode) throws MalformedURLException, IOException {
         String urlString = VARIATIONS_SERVER_URL;
+        switch (platform) {
+            case ANDROID:
+                urlString += "android";
+                break;
+            case ANDROID_WEBVIEW:
+                urlString += "android_webview";
+                break;
+            default:
+                assert false;
+        }
         if (restrictMode != null && !restrictMode.isEmpty()) {
             urlString += "&restrict=" + restrictMode;
         }
         URL url = new URL(urlString);
         return (HttpURLConnection) url.openConnection();
     }
 
     /**
+     * Store the seed and its related header fields
+     */
+    public static class SeedInfo {
+        public String signature;
+        public String country;
+        public String date;
+        public boolean isGzipCompressed;
+        public byte[] rawSeed;
+    }
+
+    /**
      * 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);
+
+            try {
+                SeedInfo info = downloadContent(VariationsPlatform.ANDROID, restrictMode);
+                VariationsSeedBridge.setVariationsFirstRunSeed(info.rawSeed, info.signature,
+                        info.country, info.date, info.isGzipCompressed);
+            } catch (IOException e) {
+                // Exceptions are handled in the downloadContent function and rethrowing the
+                // exception is to stop the normal logic flow after it, so no error-handling here.
+                // Not explicitly handing SocketTimeoutException and UnknownHostException for they
+                // are both subclasses of IOException.
+            }
             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 SeedInfo downloadContent(final VariationsPlatform platform, final String restrictMode)

[Alexei Svitkine (slow), 2017/07/11 19:37:24]

Please add javadoc documenting params, return value and the exception cases.

Also, doesn't seem like the params need to be final.

[yiyuny, 2017/07/11 22:43:37]

Done.

+            throws SocketTimeoutException, UnknownHostException, IOException {
         HttpURLConnection connection = null;
+        SeedInfo info = new SeedInfo();

[Alexei Svitkine (slow), 2017/07/11 19:37:24]

Can this be constructed right above line 187?

Ideally, you could move the return info line directly after line 192 too, but
not sure if compiler will complain. If not, you could initialize it to null here
and create it inside the try.

         try {
             long startTimeMillis = SystemClock.elapsedRealtime();
-            connection = getServerConnection(restrictMode);
+            connection = getServerConnection(platform, 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;
+                throw new IOException(
+                        "HTTP error code when fetching variations seed data: " + responseCode);

[Alexei Svitkine (slow), 2017/07/11 19:37:24]

Instead of crafting a whole new string, how about re-using the same string as
Log.w().

[yiyuny, 2017/07/11 22:43:37]

Done.

             }
 
             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);
+            info.rawSeed = getRawSeed(connection);
+            info.signature = getHeaderFieldOrEmpty(connection, "X-Seed-Signature");
+            info.country = getHeaderFieldOrEmpty(connection, "X-Country");
+            info.date = getHeaderFieldOrEmpty(connection, "Date");
+            info.isGzipCompressed = getHeaderFieldOrEmpty(connection, "IM").equals("gzip");
             recordSeedFetchTime(SystemClock.elapsedRealtime() - startTimeMillis);
         } catch (SocketTimeoutException e) {
             recordFetchResultOrCode(SEED_FETCH_RESULT_TIMEOUT);
-            Log.w(TAG, "SocketTimeoutException fetching first run seed: ", e);
+            Log.w(TAG, "SocketTimeoutException timeout when fetching variations seed.", e);
+            throw e;
         } catch (UnknownHostException e) {
             recordFetchResultOrCode(SEED_FETCH_RESULT_UNKNOWN_HOST_EXCEPTION);
-            Log.w(TAG, "UnknownHostException fetching first run seed: ", e);
+            Log.w(TAG, "UnknownHostException unknown host when fetching variations seed.", e);
+            throw e;
         } catch (IOException e) {
             recordFetchResultOrCode(SEED_FETCH_RESULT_IOEXCEPTION);
-            Log.w(TAG, "IOException fetching first run seed: ", e);
+            Log.w(TAG,
+                    "IOException I/O errors while opening the connection to fetch variations seed.",
+                    e);
+            throw e;
         } finally {
             if (connection != null) {
                 connection.disconnect();
             }
         }
+        return info;
     }
 
     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();
     }
 }