android: Don't keep GSA alive if it supports account change broadcasts.

chrome/android/java/src/org/chromium/chrome/browser/gsa/GSAAccountChangeListener.java

Index: chrome/android/java/src/org/chromium/chrome/browser/gsa/GSAAccountChangeListener.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/gsa/GSAAccountChangeListener.java b/chrome/android/java/src/org/chromium/chrome/browser/gsa/GSAAccountChangeListener.java
new file mode 100644
index 0000000000000000000000000000000000000000..a9b8556df5c699d70d5e76ce68b53d85a0cb7af8
--- /dev/null
+++ b/chrome/android/java/src/org/chromium/chrome/browser/gsa/GSAAccountChangeListener.java
@@ -0,0 +1,138 @@
+// Copyright 2016 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.gsa;
+
+import android.content.BroadcastReceiver;
+import android.content.Context;
+import android.content.Intent;
+import android.content.IntentFilter;
+import android.net.Uri;
+import android.os.Bundle;
+
+import org.chromium.base.Callback;
+import org.chromium.base.ContextUtils;
+
+/**
+ * Listens to te account change notifications from GSA.
+ *
+ * Depending on GSA's version, the account change notifications are dispatched:
+ * - Through SSB_SERVICE, or
+ * - Through a Broadcast.
+ *
+ * We proceed the following way:
+ * 1. Connect to the GSA service.
+ * 2. If GSA supports the broadcast, disconnect from it, otherwise keep the old method.
+ */
+public class GSAAccountChangeListener {
+    // These are GSA constants.
+    private static final String GSA_PACKAGE_NAME = "com.google.android.googlequicksearchbox";
+    private static final String ACCOUNT_UPDATE_BROADCAST_INTENT =
+            "com.google.android.apps.now.account_update_broadcast";
+    private static final String KEY_SSB_BROADCASTS_ACCOUNT_CHANGE_TO_CHROME =
+            "ssb_service:ssb_broadcasts_account_change_to_chrome";
+    private static final String BROADCAST_INTENT_ACCOUNT_NAME_EXTRA = "account_name";
+    public static final String ACCOUNT_UPDATE_BROADCAST_PERMISSION =
+            "com.google.android.apps.now.CURRENT_ACCOUNT_ACCESS";
+
+    private static GSAAccountChangeListener sInstance;
+
+    // Reference count for the connection.
+    private int mUsersCount;
+    private GSAServiceClient mClient;
+
+    /**
+     * @return the instance of GSAAccountChangeListener.
+     */
+    public static GSAAccountChangeListener getInstance() {
+        if (sInstance == null) {
+            Context context = ContextUtils.getApplicationContext();
+            sInstance = new GSAAccountChangeListener(context);
+        }
+        return sInstance;
+    }
+
+    private GSAAccountChangeListener(Context context) {
+        Context applicationContext = context.getApplicationContext();
+        BroadcastReceiver accountChangeReceiver = new BroadcastReceiver() {
+            @Override
+            public void onReceive(Context context, Intent intent) {
+                if (!ACCOUNT_UPDATE_BROADCAST_INTENT.equals(intent.getAction())) return;
+                String accountName = intent.getStringExtra(BROADCAST_INTENT_ACCOUNT_NAME_EXTRA);
+                GSAState.getInstance(context.getApplicationContext()).setGsaAccount(accountName);
+            }
+        };
+        applicationContext.registerReceiver(accountChangeReceiver,
+                new IntentFilter(ACCOUNT_UPDATE_BROADCAST_INTENT),
+                ACCOUNT_UPDATE_BROADCAST_PERMISSION, null);
+
+        createGsaClientAndConnect(applicationContext);
+
+        // If some future version of GSA no longer broadcasts the account change
+        // notification, need to fall back to the service.
+        //
+        // The states are: USE_SERVICE and USE_BROADCAST. The initial state (when Chrome starts) is
+        // USE_SERVICE.
+        // The state transitions are:
+        // - USE_SERVICE -> USE_BROADCAST: When GSA sends a message (through the service) declaring
+        //                                 it supports the broadcasts.
+        // - USE_BROADCAST -> USE_SERVICE: When GSA is updated.
+        BroadcastReceiver gsaUpdatedReceiver = new BroadcastReceiver() {
+            @Override
+            public void onReceive(Context context, Intent intent) {
+                Uri data = intent.getData();
+                if (data == null) return;
+
+                String packageName = data.getEncodedSchemeSpecificPart();
+                if (GSA_PACKAGE_NAME.equals(packageName)) {
+                    Context applicationContext = context.getApplicationContext();
+                    // We no longer know the account, but GSA will tell us momentarily (through
+                    // the service).
+                    GSAState.getInstance(applicationContext).setGsaAccount(null);
+                    // GSA has been updated, it might no longer support the broadcast. Reconnect to
+                    // check.
+                    mClient = null;
+                    createGsaClientAndConnect(applicationContext);
+                }
+            }
+        };
+        IntentFilter filter = new IntentFilter(Intent.ACTION_PACKAGE_REPLACED);
+        filter.addDataScheme("package");
+        context.registerReceiver(gsaUpdatedReceiver, filter);
+    }
+
+    private void createGsaClientAndConnect(Context context) {
+        Callback<Bundle> onMessageReceived = new Callback<Bundle>() {
+            @Override
+            public void onResult(Bundle result) {
+                if (result.getBoolean(KEY_SSB_BROADCASTS_ACCOUNT_CHANGE_TO_CHROME)) {
+                    notifyGsaBroadcastsAccountChanges();
+                }
+            }
+        };
+        mClient = new GSAServiceClient(context, onMessageReceived);
+        mClient.connect();
+    }
+
+    /**
+     * Connects to the GSA service if GSA doesn't support notifications.
+     */
+    public void connect() {
+        if (mClient != null) mClient.connect();
+        mUsersCount++;
+    }
+
+    /**
+     * Disconnects from the GSA service if GSA doesn't support notifications.
+     */
+    public void disconnect() {
+        mUsersCount--;
+        if (mClient != null && mUsersCount == 0) mClient.disconnect();
+    }
+
+    private void notifyGsaBroadcastsAccountChanges() {
+        mClient.disconnect();
+        mClient = null;
+    }
+}