add SkCanvas constructor that explicitly creates no_config with dimensions

src/utils/SkLuaCanvas.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkLuaCanvas.h"
 #include "SkLua.h"
 
@@ skipping 55 matching lines @@
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 
 void SkLuaCanvas::pushThis() {
     SkLua(fL).pushCanvas(this);
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 
-static SkBitmap make_bm(int width, int height) {
-    SkBitmap bm;
-    bm.setConfig(SkBitmap::kNo_Config, width, height);
-    return bm;
-}
-
 SkLuaCanvas::SkLuaCanvas(int width, int height, lua_State* L, const char func[])
-    : INHERITED(make_bm(width, height))
+    : INHERITED(width, height)
     , fL(L)
     , fFunc(func) {
 }
 
 SkLuaCanvas::~SkLuaCanvas() {}
 
 int SkLuaCanvas::save(SaveFlags flags) {
     AUTO_LUA("save");
     return this->INHERITED::save(flags);
 }
@@ skipping 187 matching lines @@
                                  const SkColor colors[], SkXfermode* xmode,
                                  const uint16_t indices[], int indexCount,
                                  const SkPaint& paint) {
     AUTO_LUA("drawVertices");
     lua.pushPaint(paint, "paint");
 }
 
 void SkLuaCanvas::drawData(const void* data, size_t length) {
     AUTO_LUA("drawData");
 }