Make SelectionState enum class

third_party/WebKit/Source/core/layout/api/SelectionStateTest.cpp

 // Copyright 2017 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 "core/layout/api/SelectionState.h"
 
 #include <sstream>
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace blink {
 
 TEST(SelectionStateTest, StreamOutput) {
   // Just explicitly sanity check a couple of values.
   {
     std::stringstream string_stream;
-    string_stream << SelectionNone;
+    string_stream << SelectionState::kNone;
     EXPECT_EQ("None", string_stream.str());
   }
   {
     std::stringstream string_stream;
-    string_stream << SelectionBoth;
+    string_stream << SelectionState::kStartAndEnd;
     EXPECT_EQ("Both", string_stream.str());
   }
 }
 
 }  // namespace blink