Add AwVariationsSeedFetchService and refactory VariationsSeedFetcher

components/variations/android/junit/src/org/chromium/components/variations/firstrun/VariationsSeedFetcherTest.java

 // Copyright 2017 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 static org.hamcrest.CoreMatchers.equalTo;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertThat;
 import static org.junit.Assert.assertTrue;
@@ skipping 35 matching lines @@
     private SharedPreferences mPrefs;
 
     @Before
     public void setUp() throws IOException {
         ContextUtils.initApplicationContextForTests(RuntimeEnvironment.application);
         // Pretend we are not on the UI thread, since the class we are testing is supposed to run
         // only on a background thread.
         ThreadUtils.setUiThread(mock(Looper.class));
         mFetcher = spy(VariationsSeedFetcher.get());
         mConnection = mock(HttpURLConnection.class);
-        doReturn(mConnection).when(mFetcher).getServerConnection("");
+        doReturn(mConnection)
+                .when(mFetcher)
+                .getServerConnection(VariationsSeedFetcher.VariationsPlatform.ANDROID, "");
         mPrefs = ContextUtils.getAppSharedPreferences();
         mPrefs.edit().clear().apply();
     }
 
     @After
     public void tearDown() {
         ThreadUtils.setUiThread(null);
     }
 
     /**
@@ skipping 58 matching lines @@
     @Test
     public void testFetchSeed_IOException() throws IOException {
         doThrow(new IOException()).when(mConnection).connect();
 
         mFetcher.fetchSeed("");
 
         assertTrue(mPrefs.getBoolean(VariationsSeedFetcher.VARIATIONS_INITIALIZED_PREF, false));
         assertFalse(VariationsSeedBridge.hasJavaPref());
     }
 }