experimental/skp_to_pdf_md5 optionally also outputs pdf files

gyp/experimental.gyp

 # GYP file to build experimental directory.
 {
   'targets': [
     {
       'target_name': 'experimental',
       'type': 'static_library',
       'include_dirs': [
         '../include/config',
         '../include/core',
       ],
@@ skipping 75 matching lines @@
         'pdf.gyp:pdf',
         'tools.gyp:proc_stats',
         'tools.gyp:sk_tool_utils',
       ],
     },
     {
       'target_name': 'skp_to_pdf_md5',
       'type': 'executable',
       'sources': [
         '../experimental/tools/skp_to_pdf_md5.cpp',
+        '../experimental/tools/SkDmuxWStream.cpp',
       ],
       'include_dirs': [
         '../src/core',
         '../tools/flags',
       ],
       'dependencies': [
         'pdf.gyp:pdf',
         'skia_lib.gyp:skia_lib',
         'tools.gyp:sk_tool_utils',
       ],
@@ skipping 15 matching lines @@
       'dependencies': [
         'skia_lib.gyp:skia_lib',
         'tools.gyp:resources',
         'tools.gyp:sk_tool_utils',
         'gputest.gyp:skgputest',
       ],
       'includes': [ 'gmslides.gypi', ],
     },
   ],
 }