Add minimal CalculateIdleState implementation for Android.

chrome/browser/idle_android.cc

+// Copyright (c) 2012 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.
+
+#include "base/logging.h"
+#include "chrome/browser/idle.h"
+
+// This currently just reports that we're active on Android. Further
+// revisions could check device state to see if we're active but on memory
+// constrained devices such as Android we'll often get completely killed if
+// Chrome isn't active anyway.
+// TODO(yfriedman): Tracking in bug: 114481
+void CalculateIdleState(unsigned int idle_threshold, IdleCallback notify) {
+  NOTIMPLEMENTED();
+  notify.Run(IDLE_STATE_ACTIVE);
+}