Add a SymbolsIterator to aid with Symbols Segmentation

third_party/WebKit/Source/platform/fonts/SymbolsIterator.h

+// 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 SymbolsIterator_h
+#define SymbolsIterator_h
+
+#include "platform/fonts/FontFallbackPriority.h"
+#include "platform/fonts/FontOrientation.h"
+#include "platform/fonts/ScriptRunIterator.h"
+#include "platform/fonts/UTF16TextIterator.h"
+#include "wtf/Allocator.h"
+#include "wtf/Noncopyable.h"
+
+namespace blink {
+
+class PLATFORM_EXPORT SymbolsIterator {
+    USING_FAST_MALLOC(SymbolsIterator);
+    WTF_MAKE_NONCOPYABLE(SymbolsIterator);
+public:
+    SymbolsIterator(const UChar* buffer, unsigned bufferSize);
+
+    bool consume(unsigned* symbolsLimit, FontFallbackPriority*);
+
+private:
+    FontFallbackPriority fontFallbackPriorityForCharacter(UChar32);
+
+    OwnPtr<UTF16TextIterator> m_utf16Iterator;
+    unsigned m_bufferSize;
+    UChar32 m_nextChar;
+    bool m_atEnd;
+
+    FontFallbackPriority m_currentFontFallbackPriority;
+    FontFallbackPriority m_previousFontFallbackPriority;
+};
+
+} // namespace blink
+
+#endif