[Android] Add test that asserts screen is on.

content/shell/android/javatests/src/org/chromium/content_shell/ContentShellPreconditionsTest.java

+// 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.
+
+package org.chromium.content_shell;
+
+import android.content.Context;
+import android.os.PowerManager;
+import android.test.suitebuilder.annotation.Smoke;
+
+import org.chromium.base.test.util.Feature;
+
+/**
+ * Test that verifies preconditions for tests to run.
+ */
+public class ContentShellPreconditionsTest extends ContentShellTestBase {
+    @Smoke
+    @Feature({"TestInfrastructure"})
+    public void testScreenIsOn() throws Exception {
+        PowerManager pm = (PowerManager) getInstrumentation().getContext().getSystemService(
+                Context.POWER_SERVICE);
+
+        assertTrue("Many tests will fail if the screen is not on.", pm.isScreenOn());
+    }
+}