Introduce ForwardCodePointStateMachine to traverse chars in code points

third_party/WebKit/Source/core/editing/state_machines/ForwardCodePointStateMachine.h

Index: third_party/WebKit/Source/core/editing/state_machines/ForwardCodePointStateMachine.h
diff --git a/third_party/WebKit/Source/core/editing/state_machines/ForwardCodePointStateMachine.h b/third_party/WebKit/Source/core/editing/state_machines/ForwardCodePointStateMachine.h
new file mode 100644
index 0000000000000000000000000000000000000000..037292bcee9d9d6e67718269ef0cf865854397c6
--- /dev/null
+++ b/third_party/WebKit/Source/core/editing/state_machines/ForwardCodePointStateMachine.h
@@ -0,0 +1,52 @@
+// 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.
+
+#ifndef ForwardCodePointStateMachine_h
+#define ForwardCodePointStateMachine_h
+
+#include "core/CoreExport.h"
+#include "core/editing/state_machines/TextSegmentationMachineState.h"
+#include "wtf/Allocator.h"
+#include "wtf/Noncopyable.h"
+#include "wtf/text/Unicode.h"
+
+namespace blink {
+
+class CORE_EXPORT ForwardCodePointStateMachine {
+  STACK_ALLOCATED();
+  WTF_MAKE_NONCOPYABLE(ForwardCodePointStateMachine);
+
+ public:
+  ForwardCodePointStateMachine();
+  ~ForwardCodePointStateMachine() = default;
+
+  // Prepares by feeding preceding text.
+  TextSegmentationMachineState feedPrecedingCodeUnit(UChar codeUnit);
+
+  // Finds boundary offset by feeding following text.
+  TextSegmentationMachineState feedFollowingCodeUnit(UChar codeUnit);
+
+  // Returns true if we are at code point boundary.
+  bool atCodePointBoundary();
+
+  // Returns the next boundary offset.
+  int getBoundaryOffset();
+
+  // Resets the internal state to the initial state.
+  void reset();
+
+ private:
+  enum class ForwardCodePointState;
+
+  // The number of code units to be deleted.
+  // Nothing to delete if there is an invalid surrogate pair.
+  int m_codeUnitsToBeDeleted = 0;
+
+  // The internal state.
+  ForwardCodePointState m_state;
+};
+
+}  // namespace blink
+
+#endif