Remove uses of SkImageDecoder from gms

gm/showmiplevels.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 "SkBitmapScaler.h"
 #include "SkGradientShader.h"
 #include "SkTypeface.h"
-#include "SkImageDecoder.h"
 #include "SkStream.h"
 #include "SkPaint.h"
 #include "SkMipMap.h"
 #include "Resources.h"
 #include "sk_tool_utils.h"
 
 #define SHOW_MIP_COLOR  0xFF000000
 
 static SkBitmap make_bitmap(int w, int h) {
     SkBitmap bm;
@@ skipping 277 matching lines @@
         }
     }
     
 private:
     typedef skiagm::GM INHERITED;
 };
 DEF_GM( return new ShowMipLevels2(255, 255); )
 DEF_GM( return new ShowMipLevels2(256, 255); )
 DEF_GM( return new ShowMipLevels2(255, 256); )
 DEF_GM( return new ShowMipLevels2(256, 256); )