Add AwVariationsSeedFetchService and refactory VariationsSeedFetcher

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

Index: components/variations/android/java/src/org/chromium/components/variations/firstrun/VariationsSeedFetcher.java
diff --git a/components/variations/android/java/src/org/chromium/components/variations/firstrun/VariationsSeedFetcher.java b/components/variations/android/java/src/org/chromium/components/variations/firstrun/VariationsSeedFetcher.java
index b02c6f1adf8d27000ab71e6a0838fbf1c3162402..16f5fbd16ce431bd381d6de1b3a1d9d9ff048a94 100644
--- a/components/variations/android/java/src/org/chromium/components/variations/firstrun/VariationsSeedFetcher.java
+++ b/components/variations/android/java/src/org/chromium/components/variations/firstrun/VariationsSeedFetcher.java
@@ -4,7 +4,6 @@
 
 package org.chromium.components.variations.firstrun;
 
-import android.content.Context;
 import android.content.SharedPreferences;
 import android.os.SystemClock;
 
@@ -30,8 +29,11 @@ import java.util.concurrent.TimeUnit;
  */
 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
@@ -47,7 +49,7 @@ public class VariationsSeedFetcher {
     @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;
@@ -77,9 +79,19 @@ public class VariationsSeedFetcher {
     }
 
     @VisibleForTesting
-    protected HttpURLConnection getServerConnection(String restrictMode)
-            throws MalformedURLException, IOException {
+    protected HttpURLConnection getServerConnection(VariationsPlatform platform,
+            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;
         }
@@ -87,6 +99,17 @@ public class VariationsSeedFetcher {
         return (HttpURLConnection) url.openConnection();
     }
 
+    /**
+     * Store the seed and its related header fields.

[Alexei Svitkine (slow), 2017/07/12 15:52:50]

Nit: Don't use the word "Store" because that's ambiguous. It may imply that it's
actually being stored somewhere, whereas it's really used as a return value.

How about:

"Object holding the seed data and related fields retrieved from HTTP headers."

[yiyuny, 2017/07/12 18:31:30]

Done.

+     */
+    public static class SeedInfo {
+        public String signature;
+        public String country;
+        public String date;
+        public boolean isGzipCompressed;
+        public byte[] rawSeed;

[Alexei Svitkine (slow), 2017/07/12 15:52:50]

Nit: Maybe seedData?

[yiyuny, 2017/07/12 18:31:30]

Done.

+    }
+
     /**
      * Fetch the first run variations seed.
      * @param restrictMode The restrict mode parameter to pass to the server via a URL param.
@@ -95,7 +118,6 @@ public class VariationsSeedFetcher {
         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
@@ -106,7 +128,17 @@ public class VariationsSeedFetcher {
                     || 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();
         }
     }
@@ -130,11 +162,23 @@ public class VariationsSeedFetcher {
         histogram.record(timeDeltaMillis);
     }
 
-    private void downloadContent(Context context, String restrictMode) {
+    /**
+     * Actually download the variations seed data with platform and retrictMode

[Alexei Svitkine (slow), 2017/07/12 15:52:50]

Nit: "Actually" doesn't add much, so just start with "Download". Also add a . at
the end.

[yiyuny, 2017/07/12 18:31:30]

Done.

+     * @param platform The platform parameter to let server only return experiments which can be
+     * runned on the platform.

[Alexei Svitkine (slow), 2017/07/12 15:52:50]

"can be run on that platform"

[yiyuny, 2017/07/12 18:31:30]

Done.

+     * @param restrictMode The restrict mode parameter to pass to the server via a URL param.
+     * @throws SocketTimeoutException when fetching seed connection times out.
+     * @throws UnknownHostException when fetching seed connection has an unknown host.
+     * @throws IOException when response code is not HTTP_OK or transmission fails on the open
+     * connection.
+     */
+    public SeedInfo downloadContent(VariationsPlatform platform, String restrictMode)
+            throws SocketTimeoutException, UnknownHostException, IOException {
         HttpURLConnection connection = null;
+        SeedInfo info = null;
         try {
             long startTimeMillis = SystemClock.elapsedRealtime();
-            connection = getServerConnection(restrictMode);
+            connection = getServerConnection(platform, restrictMode);
             connection.setReadTimeout(READ_TIMEOUT);
             connection.setConnectTimeout(REQUEST_TIMEOUT);
             connection.setDoInput(true);
@@ -143,29 +187,35 @@ public class VariationsSeedFetcher {
             int responseCode = connection.getResponseCode();
             recordFetchResultOrCode(responseCode);
             if (responseCode != HttpURLConnection.HTTP_OK) {
-                Log.w(TAG, "Non-OK response code = %d", responseCode);
-                return;
+                String errorMsg = "Non-OK response code = " + responseCode;
+                Log.w(TAG, errorMsg);
+                throw new IOException(errorMsg);
             }
 
             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 = new SeedInfo();
+            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);
+            return info;
         } 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();