[Sync] Introduce GmsCoreSyncListener.

chrome/android/sync_shell/javatests/src/org/chromium/chrome/browser/sync/FakeServerHelper.java

Index: chrome/android/sync_shell/javatests/src/org/chromium/chrome/browser/sync/FakeServerHelper.java
diff --git a/chrome/android/sync_shell/javatests/src/org/chromium/chrome/browser/sync/FakeServerHelper.java b/chrome/android/sync_shell/javatests/src/org/chromium/chrome/browser/sync/FakeServerHelper.java
index a2b1df3fbb635c8324cd9769db7a80090a88955f..18dd57332a31f24627ea2e6b9dd14bb4c7a8a416 100644
--- a/chrome/android/sync_shell/javatests/src/org/chromium/chrome/browser/sync/FakeServerHelper.java
+++ b/chrome/android/sync_shell/javatests/src/org/chromium/chrome/browser/sync/FakeServerHelper.java
@@ -361,6 +361,19 @@ public class FakeServerHelper {
         });
     }
 
+    /**
+     * Clear the server data (perform dashboard stop and clear).
+     */
+    public void clearServerData() {
+        checkFakeServerInitialized("useFakeServer must be called before clearing data");
+        ThreadUtils.runOnUiThreadBlocking(new Runnable() {
+            @Override
+            public void run() {
+                nativeClearServerData(mNativeFakeServerHelperAndroid, sNativeFakeServer);
+            }
+        });
+    }
+
     private static void checkFakeServerInitialized(String failureMessage) {
         if (sNativeFakeServer == 0L) {
             throw new IllegalStateException(failureMessage);
@@ -399,4 +412,6 @@ public class FakeServerHelper {
             long nativeFakeServerHelperAndroid, long nativeFakeServer);
     private native void nativeDeleteEntity(
             long nativeFakeServerHelperAndroid, long nativeFakeServer, String id);
+    private native void nativeClearServerData(
+            long nativeFakeServerHelperAndroid, long nativeFakeServer);
 }