Fix png encoding in skia debugger

gyp/gmslides.gypi

 # 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 this gypi to include all the golden master slides.
 {
   'include_dirs': [
     '../gm',
     # include dirs needed by particular GMs
     '../include/client/android',
@@ skipping 18 matching lines @@
         '../tools/debugger/SkDebugCanvas.cpp',
         '../tools/debugger/SkJsonWriteBuffer.h',
         '../tools/debugger/SkJsonWriteBuffer.cpp',
         '../tools/debugger/SkObjectParser.h',
         '../tools/debugger/SkObjectParser.cpp',
         '../tools/debugger/SkOverdrawMode.h',
         '../tools/debugger/SkOverdrawMode.cpp',
       ],
       'dependencies': [
         'libpng.gyp:libpng',
+        'tools.gyp:picture_utils',
       ]
     }],
   ],
 }