add SkCanvas constructor that explicitly creates no_config with dimensions

include/core/SkCanvas.h

 
 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #ifndef SkCanvas_DEFINED
@@ skipping 31 matching lines @@
     While the Canvas holds the state of the drawing device, the state (style)
     of the object being drawn is held by the Paint, which is provided as a
     parameter to each of the draw() methods. The Paint holds attributes such as
     color, typeface, textSize, strokeWidth, shader (e.g. gradients, patterns),
     etc.
 */
 class SK_API SkCanvas : public SkRefCnt {
 public:
     SK_DECLARE_INST_COUNT(SkCanvas)
 
+    /**
+     *  Creates an empty canvas with no backing device/pixels, and zero
+     *  dimensions.
+     */
     SkCanvas();
 
+    /**
+     *  Creates a canvas of the specified dimensions, but explicitly not backed
+     *  by any device/pixels. Typically this use used by subclasses who handle
+     *  the draw calls in some other way.
+     */
+    SkCanvas(int width, int height);
+
     /** Construct a canvas with the specified device to draw into.
 
         @param device   Specifies a device for the canvas to draw into.
     */
     explicit SkCanvas(SkBaseDevice* device);
 
     /** Construct a canvas with the specified bitmap to draw into.
         @param bitmap   Specifies a bitmap for the canvas to draw into. Its
                         structure are copied to the canvas.
     */
@@ skipping 1122 matching lines @@
             fCanvas->endCommentGroup();
         }
     }
 
 private:
     SkCanvas* fCanvas;
 };
 #define SkAutoCommentBlock(...) SK_REQUIRE_LOCAL_VAR(SkAutoCommentBlock)
 
 #endif