Misc: Don't run etc1 bench with invalid image and fix VS2015 build warning

bench/ETCBitmapBench.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "Benchmark.h"
 #include "Resources.h"
 #include "SkCanvas.h"
@@ skipping 105 matching lines @@
 };
 
 // This is the rendering benchmark. Prior to rendering the data, create a
 // bitmap using the etc1 data.
 class ETCBitmapBench : public ETCBitmapBenchBase {
 public:
     ETCBitmapBench(bool decompress, Backend backend)
         : fDecompress(decompress), fBackend(backend) { }
 
     bool isSuitableFor(Backend backend) override {
-        return backend == this->fBackend;
+        return SkToBool(fImage) && backend == this->fBackend;
     }
 
 protected:
     const char* onGetName() override {
         if (kGPU_Backend == this->fBackend) {
             if (this->fDecompress) {
                 return "etc1bitmap_render_gpu_decompressed";
             } else {
                 return "etc1bitmap_render_gpu_compressed";
             }
@@ skipping 89 matching lines @@
 DEF_BENCH(return new ETCBitmapBench(false, Benchmark::kGPU_Backend);)
 DEF_BENCH(return new ETCBitmapBench(true, Benchmark::kGPU_Backend);)
 
 DEF_BENCH(return new ETCBitmapUploadBench(false, Benchmark::kRaster_Backend);)
 DEF_BENCH(return new ETCBitmapUploadBench(true, Benchmark::kRaster_Backend);)
 
 DEF_BENCH(return new ETCBitmapUploadBench(false, Benchmark::kGPU_Backend);)
 DEF_BENCH(return new ETCBitmapUploadBench(true, Benchmark::kGPU_Backend);)
 
 #endif  // SK_IGNORE_ETC1_SUPPORT