Add copy (when needed) to SkGpuDevice::asSpecial

src/gpu/SkGpuDevice.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkGpuDevice.h"
 
 #include "GrBlurUtils.h"
@@ skipping 1384 matching lines @@
             return;
         }
     }
     GrBitmapTextureMaker maker(fContext, bitmap);
     this->drawTextureProducer(&maker, src, dst, constraint, *draw.fMatrix, fClip, paint);
 }
 
 sk_sp<SkSpecialImage> SkGpuDevice::asSpecial() {
     sk_sp<GrTexture> texture(this->accessDrawContext()->asTexture());
     if (!texture) {
-        return nullptr;
+        // When the device doesn't have a texture, we create a temporary texture.
+        // TODO: we should actually only copy the portion of the source needed to apply the image
+        // filter
+        texture.reset(fContext->textureProvider()->createTexture(this->accessDrawContext()->desc(),
+                                                                 SkBudgeted::kYes));
+        if (!texture) {
+            return nullptr;
+        }
+
+        if (!fContext->copySurface(this->accessDrawContext()->accessRenderTarget(),
+                                   texture.get())) {
+            return nullptr;
+        }
     }
 
     const SkImageInfo ii = this->imageInfo();
     const SkIRect srcRect = SkIRect::MakeWH(ii.width(), ii.height());
 
     return SkSpecialImage::MakeFromGpu(srcRect,
                                        kNeedNewImageUniqueID_SpecialImage,
                                        std::move(texture), 
                                        &this->surfaceProps());
 }
@@ skipping 432 matching lines @@
 }
 
 SkImageFilterCache* SkGpuDevice::getImageFilterCache() {
     ASSERT_SINGLE_OWNER
     // We always return a transient cache, so it is freed after each
     // filter traversal.
     return SkImageFilterCache::Create(kDefaultImageFilterCacheSize);
 }
 
 #endif