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..a960c55004bdca976008ce0f8b05d1bdd4970c7a 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(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;
         }
@@ -87,6 +99,17 @@ public class VariationsSeedFetcher {
         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.
@@ -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 +162,13 @@ public class VariationsSeedFetcher {
         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);
@@ -144,33 +178,38 @@ public class VariationsSeedFetcher {
             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) {