Make SkTextBlob::RunIterator public.

src/core/SkTextBlobRunIterator.h

+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+#ifndef SkTextBlobRunIterator_DEFINED
+#define SkTextBlobRunIterator_DEFINED
+
+#include "SkTextBlob.h"
+
+/**
+ *  Iterate through all of the text runs of the text blob.  For example:
+ *    for (SkTextBlobRunIterator it(blob); !it.done(); it.next()) {
+ *         .....
+ *    }
+ */
+class SkTextBlobRunIterator {
+public:
+    SkTextBlobRunIterator(const SkTextBlob* blob);
+
+    bool done() const;
+    void next();
+
+    uint32_t glyphCount() const;
+    const uint16_t* glyphs() const;
+    const SkScalar* pos() const;
+    const SkPoint& offset() const;
+    void applyFontToPaint(SkPaint*) const;
+    SkTextBlob::GlyphPositioning positioning() const;
+    bool isLCD() const;
+
+private:
+    const SkTextBlob::RunRecord* fCurrentRun;
+    int fRemainingRuns;
+
+    SkDEBUGCODE(uint8_t* fStorageTop;)
+};
+
+#endif  // SkTextBlobRunIterator_DEFINED