SkString: remove externally unused ::setUTF16() from API

Moved to SkStringUtils in src/

Change-Id: I026e3a325570bbf34e90797d921cb2f05b9a29f6
Reviewed-on: https://skia-review.googlesource.com/111602
Commit-Queue: Hal Canary <halcanary@google.com>
Reviewed-by: Ben Wagner <bungeman@google.com>
diff --git a/src/utils/SkLuaCanvas.cpp b/src/utils/SkLuaCanvas.cpp
index 9d2e8c9..53e462a 100644
--- a/src/utils/SkLuaCanvas.cpp
+++ b/src/utils/SkLuaCanvas.cpp
@@ -6,7 +6,9 @@
  */
 
 #include "SkLuaCanvas.h"
+
 #include "SkLua.h"
+#include "SkStringUtils.h"
 
 extern "C" {
     #include "lua.h"
@@ -51,11 +53,9 @@
         case SkPaint::kUTF8_TextEncoding:
             this->pushString((const char*)text, length, "text");
             break;
-        case SkPaint::kUTF16_TextEncoding: {
-            SkString str;
-            str.setUTF16((const uint16_t*)text, length);
-            this->pushString(str, "text");
-        } break;
+        case SkPaint::kUTF16_TextEncoding:
+            this->pushString(SkStringFromUTF16((const uint16_t*)text, length), "text");
+            break;
         case SkPaint::kGlyphID_TextEncoding:
             this->pushArrayU16((const uint16_t*)text, SkToInt(length >> 1),
                                "glyphs");