Remove uses of SkImageDecoder from gms

gm/avoidxfermode.cpp

 /*
  * Copyright 2016 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 "Resources.h"
 
-#include "SkImageDecoder.h"
 #include "SkAvoidXfermode.h"
 #include "SkStream.h"
 
 class AvoidXfermodeGM : public skiagm::GM {
 public:
     AvoidXfermodeGM() { }
 
 protected:
     SkString onShortName() override {
         return SkString("avoidxfermode");
     }
 
     SkISize onISize() override { return SkISize::Make(128, 128); }
 
     void onOnceBeforeDraw() override {
-        SkImageDecoder* codec = nullptr;
-        SkString resourcePath = GetResourcePath("color_wheel.png");
-        SkFILEStream stream(resourcePath.c_str());
-        if (stream.isValid()) {
-            codec = SkImageDecoder::Factory(&stream);
-        }
-        if (codec) {
-            stream.rewind();
-            codec->decode(&stream, &fBM, kN32_SkColorType, SkImageDecoder::kDecodePixels_Mode);
-            delete codec;
-        } else {
+        if (!GetResourceAsBitmap("color_wheel.png", &fBM)) {
             fBM.allocN32Pixels(1, 1);
             fBM.eraseARGB(255, 255, 0 , 0); // red == bad
         }
     }
 
     void onDraw(SkCanvas* canvas) override {
         canvas->drawBitmap(fBM, 0, 0);
 
         SkRect r = SkRect::MakeIWH(64, 64);
 
@@ skipping 42 matching lines @@
 
 private:
     SkBitmap fBM;
 
     typedef GM INHERITED;
 };
 
 //////////////////////////////////////////////////////////////////////////////
 
 DEF_GM(return new AvoidXfermodeGM;)