Add a service to handle postMessage callbacks to client

customtabs/src/android/support/customtabs/PostMessageServiceConnection.java

Index: customtabs/src/android/support/customtabs/PostMessageServiceConnection.java
diff --git a/customtabs/src/android/support/customtabs/PostMessageServiceConnection.java b/customtabs/src/android/support/customtabs/PostMessageServiceConnection.java
new file mode 100644
index 0000000000000000000000000000000000000000..4eef50c7e11e238cea71ca5d9f3cd5fd463af20c
--- /dev/null
+++ b/customtabs/src/android/support/customtabs/PostMessageServiceConnection.java
@@ -0,0 +1,126 @@
+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package android.support.customtabs;
+
+import android.content.ComponentName;
+import android.content.Context;
+import android.content.Intent;
+import android.content.ServiceConnection;
+import android.os.Bundle;
+import android.os.IBinder;
+import android.os.RemoteException;
+
+/**
+ * A {@link ServiceConnection} for Custom Tabs providers to use while connecting to a
+ * {@link PostMessageService} on the client side.
+ */
+public abstract class PostMessageServiceConnection implements ServiceConnection {
+    private final Object mLock = new Object();
+    private final ICustomTabsCallback mSessionBinder;
+    private IPostMessageService mService;
+
+    public PostMessageServiceConnection(CustomTabsSessionToken session) {
+        mSessionBinder = ICustomTabsCallback.Stub.asInterface(session.getCallbackBinder());
+    }
+
+    /**
+     * Binds the browser side to the client app through the given {@link PostMessageService} name.
+     * After this, this {@link PostMessageServiceConnection} can be used for sending postMessage
+     * related communication back to the client.
+     * @param context A context to bind to the service.
+     * @param packageName The name of the package to be bound to.
+     * @return Whether the binding was successful.
+     */
+    public boolean bindSessionToPostMessageService(Context context, String packageName) {
+        Intent intent = new Intent();
+        intent.setClassName(packageName, PostMessageService.class.getName());
+        return context.bindService(intent, this, Context.BIND_AUTO_CREATE);
+    }
+
+    /**
+     * Unbinds this service connection from the given context.
+     * @param context The context to be unbound from.
+     */
+    public void unbindFromContext(Context context) {
+        context.unbindService(this);
+    }
+
+    @Override
+    public final void onServiceConnected(ComponentName name, IBinder service) {
+        mService = IPostMessageService.Stub.asInterface(service);
+        onPostMessageServiceConnected();
+    }
+
+    @Override
+    public final void onServiceDisconnected(ComponentName name) {
+        mService = null;
+        onPostMessageServiceDisconnected();
+    }
+
+    /**
+     * Notifies the client that the postMessage channel requested with
+     * {@link CustomTabsService#requestPostMessageChannel(
+     * CustomTabsSessionToken, android.net.Uri)} is ready. This method should be
+     * called when the browser binds to the client side {@link PostMessageService} and also readies
+     * a connection to the web frame.
+     *
+     * @param extras Reserved for future use.
+     * @return Whether the notification was sent to the remote successfully.
+     */
+    public final boolean notifyMessageChannelReady(Bundle extras) {
+        if (mService == null) return false;
+        synchronized (mLock) {
+            try {
+                mService.onMessageChannelReady(mSessionBinder, extras);
+            } catch (RemoteException e) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    /**
+     * Posts a message to the client. This should be called when a tab controlled by related
+     * {@link CustomTabsSession} has sent a postMessage. If postMessage() is called from a single
+     * thread, then the messages will be posted in the same order.
+     *
+     * @param message The message sent.
+     * @param extras Reserved for future use.
+     * @return Whether the postMessage was sent to the remote successfully.
+     */
+    public final boolean postMessage(String message, Bundle extras) {
+        if (mService == null) return false;
+        synchronized (mLock) {
+            try {
+                mService.onPostMessage(mSessionBinder, message, extras);
+            } catch (RemoteException e) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    /**
+     * Called when the {@link PostMessageService} connection is established.
+     */
+    public void onPostMessageServiceConnected() {}
+
+    /**
+     * Called when the connection is lost with the {@link PostMessageService}.
+     */
+    public void onPostMessageServiceDisconnected() {}
+}