Eliminate one copy of replace_char() function.

include/core/SkString.h

Index: include/core/SkString.h
diff --git a/include/core/SkString.h b/include/core/SkString.h
index 8a962ae67142585e22097579dce68b9da0f0cfef..64b3b59b8ca0541b21615ae5b9e9f6d31a61f544 100644
--- a/include/core/SkString.h
+++ b/include/core/SkString.h
@@ -199,6 +199,8 @@ public:
 
     void remove(size_t offset, size_t length);
 
+    void replace(SkUnichar oldChar, SkUnichar newChar);
+
     SkString& operator+=(const SkString& s) { this->append(s); return *this; }
     SkString& operator+=(const char text[]) { this->append(text); return *this; }
     SkString& operator+=(const char c) { this->append(&c, 1); return *this; }