Don't copy image buffer when calculating size.

src/image/SkImage_Gpu.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 <cstddef>
 #include <cstring>
 #include <type_traits>
@@ skipping 467 matching lines @@
     size_t ctSize = 0;
     int ctCount = 0;
     if (!isScaled && this->peekPixels(&pixmap)) {
         info = pixmap.info();
         pixelSize = SkAlign8(pixmap.getSafeSize());
         if (pixmap.ctable()) {
             ctCount = pixmap.ctable()->count();
             ctSize = SkAlign8(pixmap.ctable()->count() * 4);
         }
     } else {
-        // Here we're just using presence of data to know whether there is a codec behind the image.
-        // In the future we will access the cacherator and get the exact data that we want to (e.g.
-        // yuv planes) upload.
-        sk_sp<SkData> data(this->refEncoded());
-        if (!data && !this->peekPixels(nullptr)) {
+        if (!as_IB(this)->canGenerateTexture(proxy)) {

[reed1, 2016/10/24 13:42:00]

Is the predicate reversed here? If the image *can* generate a texture, than we
should just return (nothing CPU expensive to cache). If it cannot, then we
should proceed with extracting its pixels...

[cblume, 2016/10/25 02:51:01]

Done.

             return 0;
         }
         info = as_IB(this)->onImageInfo().makeWH(scaledSize.width(), scaledSize.height());
         pixelSize = SkAlign8(SkAutoPixmapStorage::AllocSize(info, nullptr));
         if (fillMode) {
             pixmap.alloc(info);
             if (isScaled) {
                 if (!this->scalePixels(pixmap, scaleFilterQuality,
                                        SkImage::kDisallow_CachingHint)) {
                     return 0;
@@ skipping 201 matching lines @@
     }
     SkAutoTUnref<GrTexture> texture(GrUploadMipMapToTexture(ctx, info, texels, mipLevelCount));
     if (!texture) {
         return nullptr;
     }
     texture->texturePriv().setGammaTreatment(gammaTreatment);
     return sk_make_sp<SkImage_Gpu>(texture->width(), texture->height(), kNeedNewImageUniqueID,
                                    info.alphaType(), texture, sk_ref_sp(info.colorSpace()),
                                    budgeted);
 }