Revert of Make nanobench and dm be usable from Chromium build

gyp/dm.gyp

 # GYP for "dm" (Diamond Master, a.k.a Dungeon master, a.k.a GM 2).
 {
     'includes': [ 'apptype_console.gypi' ],
 
     'targets': [{
         'target_name': 'dm',
         'type': 'executable',
         'includes': [
           'dm.gypi',
         ],
-        'sources': [
-          '../dm/dm_main.cpp',
-        ],
         'conditions': [
           ['skia_android_framework', {
               'libraries': [ '-lskia' ],
           }],
           ['skia_poppler_enabled', {
               'sources':      [ '../src/utils/SkPDFRasterizer.cpp' ],
               'defines':      [ 'SK_BUILD_POPPLER' ],
               'dependencies': [ 'poppler.gyp:*' ],
           }],
         ],
     }]
 }