Move test-only ContextFactory implementations out of production targets

ui/compositor/test/context_factories_for_test.h

+// Copyright (c) 2013 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.
+
+namespace ui {
+
+// Set up the compositor ContextFactory for a test environment. Unit tests
+// that do not have a full content environment need to call this before
+// initializing the Compositor.
+// Some tests expect pixel output, and they should pass false for
+// |allow_test_contexts|. Most unit tests should pass true. Once this has been
+// called, the caller must call TerminateContextFactoryForTests() to clean up.
+void InitializeContextFactoryForTests(bool allow_test_contexts);
+void TerminateContextFactoryForTests();
+
+}  // namespace ui