Move DM png code to picture_utils, for use by other tools.

gyp/tools.gyp

 # Copyright 2015 Google Inc.
 #
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
     # GYP file to build various tools.
 #
 # To build on Linux:
 #  ./gyp_skia tools.gyp && make tools
 #
 {
@@ skipping 333 matching lines @@
         'skia_lib.gyp:skia_lib',
       ],
     },
     {
       'target_name': 'picture_utils',
       'type': 'static_library',
       'sources': [
         '../tools/picture_utils.cpp',
         '../tools/picture_utils.h',
       ],
+          'include_dirs': [
+          '../src/core/',
+      ],
       'dependencies': [
         'skia_lib.gyp:skia_lib',
       ],
       'direct_dependent_settings': {
         'include_dirs': [
           '../tools/',
         ],
       },
     },
     {
@@ skipping 243 matching lines @@
               'pdf.gyp:pdf',
             ],
             'defines': [ 'FIDDLE_BUILD_TEST' ],
             'link_settings': { 'libraries': [ '-lOSMesa' ], },
           },
         ],
       },
     ],
   ],
 }