[Sync] Introduce GmsCoreSyncListener.

chrome/test/android/javatests/src/org/chromium/chrome/test/util/browser/sync/SyncTestUtil.java

Index: chrome/test/android/javatests/src/org/chromium/chrome/test/util/browser/sync/SyncTestUtil.java
diff --git a/chrome/test/android/javatests/src/org/chromium/chrome/test/util/browser/sync/SyncTestUtil.java b/chrome/test/android/javatests/src/org/chromium/chrome/test/util/browser/sync/SyncTestUtil.java
index c50ee4af2232b5bc7182ea250271c9feff113db1..9b48687820cf4d77767ef3ddc0d5c861cf7077a7 100644
--- a/chrome/test/android/javatests/src/org/chromium/chrome/test/util/browser/sync/SyncTestUtil.java
+++ b/chrome/test/android/javatests/src/org/chromium/chrome/test/util/browser/sync/SyncTestUtil.java
@@ -186,12 +186,9 @@ public final class SyncTestUtil {
     }
 
     /**
-     * Triggers a sync and waits till it is complete.
+     * Triggers a sync cycle.
      */
-    public static void triggerSyncAndWaitForCompletion(final Context context)
-            throws InterruptedException {
-        final long oldSyncTime = getCurrentSyncTime(context);
-        // Request sync.
+    public static void triggerSync() throws InterruptedException {
         ThreadUtils.runOnUiThreadBlocking(new Runnable() {
             @Override
             public void run() {
@@ -199,6 +196,16 @@ public final class SyncTestUtil {
                         .requestSyncFromNativeChromeForAllTypes();
             }
         });
+    }
+
+    /**
+     * Triggers a sync and waits till it is complete.
+     */
+    public static void triggerSyncAndWaitForCompletion(final Context context)
+            throws InterruptedException {
+        final long oldSyncTime = getCurrentSyncTime(context);
+
+        triggerSync();
 
         // Wait till lastSyncedTime > oldSyncTime.
         Assert.assertTrue("Timed out waiting for syncing to complete.",