Introduce EditingTestBase to share code among test files for editing

Source/core/editing/EditingTestBase.h

Index: Source/core/editing/EditingTestBase.h
diff --git a/Source/core/editing/EditingTestBase.h b/Source/core/editing/EditingTestBase.h
new file mode 100644
index 0000000000000000000000000000000000000000..d5dd5a75bfbf67a6756f0e027814789802e0254c
--- /dev/null
+++ b/Source/core/editing/EditingTestBase.h
@@ -0,0 +1,40 @@
+// 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.
+
+#ifndef EditingTestBase_h
+#define EditingTestBase_h
+
+#include "core/dom/Position.h"
+#include "core/testing/CoreTestHelpers.h"
+#include "wtf/Forward.h"
+#include <gtest/gtest.h>
+
+namespace blink {
+
+class DummyPageHolder;
+
+class EditingTestBase : public ::testing::Test {
+protected:
+    EditingTestBase();
+    ~EditingTestBase() override;
+
+    void SetUp() override;
+
+    Document& document() const;
+
+    static PassRefPtrWillBeRawPtr<ShadowRoot> createShadowRootForElementWithIDAndSetInnerHTML(TreeScope&, const char* hostElementID, const char* shadowRootContent);
+
+    void setBodyContent(const char*);
+    PassRefPtrWillBeRawPtr<ShadowRoot> setShadowContent(const char*);
+
+    static Position positionInDOMTree(Node& anchor, int offset);
+    static PositionInComposedTree positionInComposedTree(Node& anchor, int offset);
+
+private:
+    OwnPtr<DummyPageHolder> m_dummyPageHolder;
+};
+
+} // namespace blink
+
+#endif // EditingTestBase_h