[Sync] Introduce GmsCoreSyncListener.

chrome/android/java/src/org/chromium/chrome/browser/sync/GmsCoreSyncListener.java

Index: chrome/android/java/src/org/chromium/chrome/browser/sync/GmsCoreSyncListener.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/sync/GmsCoreSyncListener.java b/chrome/android/java/src/org/chromium/chrome/browser/sync/GmsCoreSyncListener.java
new file mode 100644
index 0000000000000000000000000000000000000000..4d3642acf33c7a43c7547bed75b169389299e189
--- /dev/null
+++ b/chrome/android/java/src/org/chromium/chrome/browser/sync/GmsCoreSyncListener.java
@@ -0,0 +1,42 @@
+// 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.sync;
+
+import org.chromium.base.VisibleForTesting;
+
+/**
+ * A listener that will share sync's custom passphrase encryption key with GmsCore.
+ *
+ * This is to prevent users from seeing the custom passphrase dialog pop up in GmsCore after they
+ * have already entered it in Chrome.
+ */
+public abstract class GmsCoreSyncListener implements ProfileSyncService.SyncStateChangedListener {
+    private boolean mGmsCoreInformed;
+
+    /**
+     * Inform GMSCore of a new custom passphrase encryption key.
+     *
+     * @param key The serialized NigoriKey proto.
+     */
+    public abstract void updateEncryptionKey(byte[] key);
+
+    @Override
+    @VisibleForTesting
+    public void syncStateChanged() {
+        ProfileSyncService syncService = ProfileSyncService.get();
+        boolean passphraseSet = syncService.isBackendInitialized()
+                && syncService.isUsingSecondaryPassphrase() && syncService.isCryptographerReady();
+        if (passphraseSet && !mGmsCoreInformed) {
+            byte[] key = syncService.getCustomPassphraseKey();
+            if (key.length > 0) {
+                updateEncryptionKey(key);
+                mGmsCoreInformed = true;
+            }
+        } else if (!passphraseSet && mGmsCoreInformed) {
+            // Prepare to inform GmsCore if a passphrase is set again.
+            mGmsCoreInformed = false;
+        }
+    }
+}