[Android] A prototype of the interactive media notification.

chrome/android/java/src/org/chromium/chrome/browser/media/ui/MediaPlaybackControls.java

Index: chrome/android/java/src/org/chromium/chrome/browser/media/ui/MediaPlaybackControls.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/media/ui/MediaPlaybackControls.java b/chrome/android/java/src/org/chromium/chrome/browser/media/ui/MediaPlaybackControls.java
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+++ b/chrome/android/java/src/org/chromium/chrome/browser/media/ui/MediaPlaybackControls.java
@@ -0,0 +1,94 @@
+// 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.media.ui;
+
+import java.util.Set;
+import java.util.concurrent.CopyOnWriteArraySet;
+
+/**
+ * MediaPlaybackControls is an abstract base class for various UI views that are intended to control
+ * media playback. MediaPlaybackControls contains a number of setters that will update the
+ * MediaPlaybackControls's UI.
+ * Call {@code MediaPlaybackControls#addListener} with an implementation of
+ * {@code MediaPlaybackControls.Listener} to receive messages when the user interacts with the
+ * controls.
+ */
+public abstract class MediaPlaybackControls implements MediaPlaybackListener {
+
+    /**
+     * Base interface for classes that need to listen to transport control events.
+     */
+    public static interface Listener {
+        void onPlay();
+        void onPause();
+    }
+
+    // Initialized lazily to simplify testing. Should only ever be accessed through getListeners to
+    // ensure correct initialization.
+    private Set<Listener> mListeners;
+    protected MediaInfo mMediaInfo;
+
+    /**
+     * @return the media information previously assigned with
+     * {@link #setMediaInfo(MediaInfo)}, or {@code null} if the {@link MediaInfo}
+     * has not yet been assigned.
+     */
+    public final MediaInfo getMediaInfo() {
+        return mMediaInfo;
+    }
+
+    /**
+     * Sets the media information to display on the MediaPlaybackControls.
+     * @param mediaInfo the media information to use.
+     */
+    public final void setMediaInfo(MediaInfo mediaInfo) {
+        if (equal(mMediaInfo, mediaInfo)) return;
+
+        mMediaInfo = mediaInfo;
+        onMediaInfoChanged();
+    }
+
+    /**
+     * Registers a {@link Listener} with the MediaPlaybackControls.
+     * @param listener the Listener to be registered.
+     */
+    public void addListener(Listener listener) {
+        getListeners().add(listener);
+    }
+
+    /**
+     * Unregisters a {@link Listener} previously registered with {@link #addListener(Listener)}.
+     * @param listener the Listener to be removed.
+     */
+    public void removeListener(Listener listener) {
+        getListeners().remove(listener);
+    }
+
+    /**
+     * Displays the MediaPlaybackControls to the user.
+     * @param mediaInfo the information about the media.
+     */
+    public abstract void show(MediaInfo mediaInfo);
+
+    /**
+     * Hides the MediaPlaybackControls.
+     * @param tabId tab that requests to hide the controls
+     */
+    public abstract void hide(int tabId);
+
+    /**
+     * @return the current list of listeners.
+     */
+    protected final Set<Listener> getListeners() {
+        if (mListeners == null) mListeners = new CopyOnWriteArraySet<Listener>();
+        return mListeners;
+    }
+
+    protected void onMediaInfoChanged() {}
+
+    private static boolean equal(Object a, Object b) {
+        return (a == null) ? (b == null) : a.equals(b);
+    }
+}