GMs: fail gracefully for null surface

gm/image_pict.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "gm.h"
 #include "SkCanvas.h"
 #include "SkImage.h"
@@ skipping 194 matching lines @@
 };
 
 #if SK_SUPPORT_GPU
 class TextureGenerator : public SkImageGenerator {
 public:
     TextureGenerator(GrContext* ctx, const SkImageInfo& info, SkPicture* pic)
         : SkImageGenerator(info)
         , fCtx(SkRef(ctx))
     {
         auto surface(SkSurface::MakeRenderTarget(ctx, SkBudgeted::kNo, info));
-        surface->getCanvas()->clear(0);
-        surface->getCanvas()->translate(-100, -100);
-        surface->getCanvas()->drawPicture(pic);
-        sk_sp<SkImage> image(surface->makeImageSnapshot());
-        fTexture.reset(SkRef(as_IB(image)->peekTexture()));
+        if (surface) {
+            surface->getCanvas()->clear(0);
+            surface->getCanvas()->translate(-100, -100);
+            surface->getCanvas()->drawPicture(pic);
+            sk_sp<SkImage> image(surface->makeImageSnapshot());
+            fTexture.reset(SkRef(as_IB(image)->peekTexture()));
+        }
     }
 protected:
     GrTexture* onGenerateTexture(GrContext* ctx, const SkIRect* subset) override {
         if (ctx) {
             SkASSERT(ctx == fCtx.get());
         }
 
+        if (!fTexture) {
+            return nullptr;
+        }
+
         if (!subset) {
             return SkRef(fTexture.get());
         }
         // need to copy the subset into a new texture
         GrSurfaceDesc desc = fTexture->desc();
         desc.fWidth = subset->width();
         desc.fHeight = subset->height();
 
         GrTexture* dst = fCtx->textureProvider()->createTexture(desc, SkBudgeted::kNo);
         fCtx->copySurface(dst, fTexture, *subset, SkIPoint::Make(0, 0));
@@ skipping 129 matching lines @@
 
 private:
     typedef skiagm::GM INHERITED;
 };
 DEF_GM( return new ImageCacheratorGM("picture", make_pic_generator); )
 DEF_GM( return new ImageCacheratorGM("raster", make_ras_generator); )
 DEF_GM( return new ImageCacheratorGM("ctable", make_ctable_generator); )
 #if SK_SUPPORT_GPU
     DEF_GM( return new ImageCacheratorGM("texture", make_tex_generator); )
 #endif