Overlay content is its own class

chrome/android/java/src/org/chromium/chrome/browser/compositor/bottombar/OverlayContentProgressObserver.java

Index: chrome/android/java/src/org/chromium/chrome/browser/compositor/bottombar/OverlayContentProgressObserver.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/compositor/bottombar/OverlayContentProgressObserver.java b/chrome/android/java/src/org/chromium/chrome/browser/compositor/bottombar/OverlayContentProgressObserver.java
new file mode 100644
index 0000000000000000000000000000000000000000..e44dafa943f27b25782e272cc015e146dcb6bf8e
--- /dev/null
+++ b/chrome/android/java/src/org/chromium/chrome/browser/compositor/bottombar/OverlayContentProgressObserver.java
@@ -0,0 +1,28 @@
+// Copyright 2015 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.compositor.bottombar;
+
+/**
+ * Default implementation of an observer of events on the progress bar.
+ */
+public class OverlayContentProgressObserver {
+
+    /**
+     * Called when the progress bar would start showing (loading started).
+     */
+    public void onProgressBarStarted() {}
+
+    /**
+     * Called when progress has updated.
+     * @param progress The current progress.
+     */
+    public void onProgressBarUpdated(int progress) {}
+
+    /**
+     * Called when the progress bar has finished.
+     */
+    public void onProgressBarFinished() {}
+}
+