[Android] Extract a TabModelSelectorObserver to make it more consistent.

chrome/android/java/src/org/chromium/chrome/browser/tabmodel/EmptyTabModelSelectorObserver.java

Index: chrome/android/java/src/org/chromium/chrome/browser/tabmodel/EmptyTabModelSelectorObserver.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/tabmodel/EmptyTabModelSelectorObserver.java b/chrome/android/java/src/org/chromium/chrome/browser/tabmodel/EmptyTabModelSelectorObserver.java
new file mode 100644
index 0000000000000000000000000000000000000000..d51c5d0ef4918e19e2f3c0fcd0cbdb51c96c5bb9
--- /dev/null
+++ b/chrome/android/java/src/org/chromium/chrome/browser/tabmodel/EmptyTabModelSelectorObserver.java
@@ -0,0 +1,22 @@
+// Copyright 2014 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.chrome.browser.tabmodel;
+
+import org.chromium.chrome.browser.Tab;
+
+/**
+ * Empty implementation of the tab model selector observer.
+ */
+public class EmptyTabModelSelectorObserver implements TabModelSelectorObserver {
+
+    @Override
+    public void onChange() {
+    }
+
+    @Override
+    public void onNewTabCreated(Tab tab) {
+    }
+
+}