[Android] A prototype of the interactive media notification.

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

Index: chrome/android/java/src/org/chromium/chrome/browser/media/ui/MediaSessionTabHelper.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/media/ui/MediaSessionTabHelper.java b/chrome/android/java/src/org/chromium/chrome/browser/media/ui/MediaSessionTabHelper.java
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+++ b/chrome/android/java/src/org/chromium/chrome/browser/media/ui/MediaSessionTabHelper.java
@@ -0,0 +1,129 @@
+// 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 org.chromium.base.ApplicationStatus;
+import org.chromium.base.Log;
+import org.chromium.chrome.browser.EmptyTabObserver;
+import org.chromium.chrome.browser.Tab;
+import org.chromium.chrome.browser.TabObserver;
+import org.chromium.chrome.browser.UrlUtilities;
+import org.chromium.content_public.browser.WebContents;
+import org.chromium.content_public.browser.WebContentsObserver;
+
+import java.net.URI;
+import java.net.URISyntaxException;
+
+/**
+ * A tab helper responsible for enabling/disabling media controls and passing
+ * media actions from the controls to the {@link org.chromium.content.browser.MediaSession}
+ */
+public class MediaSessionTabHelper {
+    private static final String TAG = "cr.MediaSession";
+
+    private Tab mTab;
+    private WebContents mWebContents;
+    private WebContentsObserver mWebContentsObserver;
+
+    private MediaPlaybackListener mControlsListener = new MediaPlaybackListener() {
+        @Override
+        public void onPlay() {
+            assert mWebContents != null;
+            mWebContents.resumeMediaSession();
+        }
+
+        @Override
+        public void onPause() {
+            assert mWebContents != null;
+            mWebContents.suspendMediaSession();
+        }
+    };
+
+    private WebContentsObserver createWebContentsObserver(WebContents webContents) {
+        return new WebContentsObserver(webContents) {
+            @Override
+            public void destroy() {
+                if (mTab == null) {
+                    NotificationMediaPlaybackControls.clear();
+                } else {
+                    NotificationMediaPlaybackControls.hide(mTab.getId());
+                }
+                super.destroy();
+            }
+
+            @Override
+            public void mediaSessionStateChanged(boolean isControllable, boolean isPaused) {
+                assert mTab != null;
+                if (!isControllable) {
+                    NotificationMediaPlaybackControls.hide(mTab.getId());
+                    return;
+                }
+                String origin = mTab.getUrl();
+                try {
+                    origin = UrlUtilities.getOriginForDisplay(new URI(origin), true);
+                } catch (URISyntaxException e) {
+                    Log.e(TAG, "Unable to parse the origin from the URL. "
+                            + "Showing the full URL instead.");
+                }
+                NotificationMediaPlaybackControls.show(
+                        ApplicationStatus.getApplicationContext(),
+                        new MediaInfo(
+                                mTab.getTitle(),
+                                isPaused,
+                                origin,
+                                mTab.getId(),
+                                mControlsListener));
+            }
+        };
+
+    }
+
+    private void setWebContents(WebContents webContents) {
+        if (mWebContents == webContents) return;
+
+        cleanupWebContents();
+        mWebContents = webContents;
+        if (mWebContents != null) mWebContentsObserver = createWebContentsObserver(mWebContents);
+    }
+
+    private void cleanupWebContents() {
+        if (mWebContentsObserver != null) mWebContentsObserver.destroy();
+        mWebContentsObserver = null;
+        mWebContents = null;
+    }
+
+    private final TabObserver mTabObserver = new EmptyTabObserver() {
+        @Override
+        public void onContentChanged(Tab tab) {
+            assert tab == mTab;
+            setWebContents(tab.getWebContents());
+        }
+
+        @Override
+        public void onDestroyed(Tab tab) {
+            assert mTab == tab;
+
+            cleanupWebContents();
+
+            NotificationMediaPlaybackControls.hide(mTab.getId());
+            mTab.removeObserver(this);
+            mTab = null;
+        }
+    };
+
+    private MediaSessionTabHelper(Tab tab) {
+        mTab = tab;
+        mTab.addObserver(mTabObserver);
+        if (mTab.getWebContents() != null) setWebContents(tab.getWebContents());
+    }
+
+    /**
+     * Creates the {@link MediaSessionTabHelper} for the given {@link Tab}.
+     * @param tab the tab to attach the helper to.
+     */
+    public static void createForTab(Tab tab) {
+        new MediaSessionTabHelper(tab);
+    }
+}