impl preroll for all image backends

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 37 matching lines @@
 bool SkImage::readPixels(const SkImageInfo& dstInfo, void* dstPixels, size_t dstRowBytes,
                            int srcX, int srcY) const {
     SkReadPixelsRec rec(dstInfo, dstPixels, dstRowBytes, srcX, srcY);
     if (!rec.trim(this->width(), this->height())) {
         return false;
     }
     return as_IB(this)->onReadPixels(rec.fInfo, rec.fPixels, rec.fRowBytes, rec.fX, rec.fY);
 }
 
 void SkImage::preroll(GrContext* ctx) const {
-    as_IB(this)->onPreroll(ctx);
+    // For now, and to maintain parity w/ previous pixelref behavior, we just force the image
+    // to produce a cached raster-bitmap form, so that drawing to a raster canvas should be fast.
+    //
+    SkBitmap bm;
+    if (as_IB(this)->getROPixels(&bm)) {
+        bm.lockPixels();
+        bm.unlockPixels();
+    }
 }
 
 SkShader* SkImage::newShader(SkShader::TileMode tileX,
                              SkShader::TileMode tileY,
                              const SkMatrix* localMatrix) const {
     return as_IB(this)->onNewShader(tileX, tileY, localMatrix);
 }
 
 SkData* SkImage::encode(SkImageEncoder::Type type, int quality) const {
     SkBitmap bm;
@@ skipping 272 matching lines @@
 
 SkImage* SkImage::NewFromAdoptedTexture(GrContext*, const GrBackendTextureDesc&, SkAlphaType) {
     return nullptr;
 }
 
 SkImage* SkImage::NewFromTextureCopy(GrContext*, const GrBackendTextureDesc&, SkAlphaType) {
     return nullptr;
 }
 
 #endif