add SkImage::NewFromPicture and a GM to test it

src/image/SkImage.cpp

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkBitmap.h"
 #include "SkCanvas.h"
 #include "SkData.h"
@@ skipping 261 matching lines @@
         bitmap->reset();
         return false;
     }
 
     if (kRO_LegacyBitmapMode == mode) {
         bitmap->setImmutable();
     }
     return true;
 }
 
+SkImage* SkImage::NewFromPicture(const SkPicture* picture, const SkISize& dimensions,
+                                 const SkMatrix* matrix, const SkPaint* paint) {
+    if (!picture) {
+        return nullptr;
+    }
+    return NewFromGenerator(SkImageGenerator::NewFromPicture(dimensions, picture, matrix, paint));
+}
+
 //////////////////////////////////////////////////////////////////////////////////////
 
 #if !SK_SUPPORT_GPU
 
 SkImage* SkImage::NewFromTexture(GrContext*, const GrBackendTextureDesc&, SkAlphaType,
                                  TextureReleaseProc, ReleaseContext) {
     return NULL;
 }
 
 SkImage* SkImage::NewFromAdoptedTexture(GrContext*, const GrBackendTextureDesc&, SkAlphaType) {
     return NULL;
 }
 
 SkImage* SkImage::NewFromTextureCopy(GrContext*, const GrBackendTextureDesc&, SkAlphaType) {
     return NULL;
 }
 
 #endif