Add AwVariationsSeedFetcher 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..66987f7daa263300dc128974a155d44db6f797ec 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;
 
@@ -23,6 +22,8 @@ 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;
 
 /**
@@ -30,8 +31,15 @@ import java.util.concurrent.TimeUnit;
  */
 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
@@ -77,9 +85,8 @@ public class VariationsSeedFetcher {
     }
 
     @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;
         }
@@ -95,7 +102,6 @@ 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 +112,18 @@ public class VariationsSeedFetcher {
                     || 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();
         }
     }
@@ -130,11 +147,13 @@ public class VariationsSeedFetcher {
         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);
@@ -144,18 +163,18 @@ public class VariationsSeedFetcher {
             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);
@@ -171,6 +190,7 @@ public class VariationsSeedFetcher {
                 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) {