add NewRasterDirect for creating a canvas drawing to pre-allocated pixels

src/core/SkCanvas.cpp

 
 /*
  * Copyright 2008 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.
  */
 
 
 #include "SkCanvas.h"
@@ skipping 2531 matching lines @@
     if (!bitmap.allocPixels(info)) {
         return NULL;
     }
 
     // should this functionality be moved into allocPixels()?
     if (!bitmap.info().isOpaque()) {
         bitmap.eraseColor(0);
     }
     return SkNEW_ARGS(SkCanvas, (bitmap));
 }
+
+SkCanvas* SkCanvas::NewRasterDirect(const SkImageInfo& info, void* pixels, size_t rowBytes) {
+    if (!supported_for_raster_canvas(info)) {
+        return NULL;
+    }
+    
+    SkBitmap bitmap;
+    if (!bitmap.installPixels(info, pixels, rowBytes)) {
+        return NULL;
+    }
+    
+    // should this functionality be moved into allocPixels()?
+    if (!bitmap.info().isOpaque()) {
+        bitmap.eraseColor(0);
+    }
+    return SkNEW_ARGS(SkCanvas, (bitmap));
+}
+
+