gm: add a flag to force perspective usage in all gms

gyp/gm.gyp

 # GYP file to build the "gm" (golden master) executable.
 {
   'includes': [
     'apptype_console.gypi',
   ],
   'targets': [
     {
       'target_name': 'gm_expectations',
       'type': 'static_library',
       'include_dirs' : [
         '../src/utils/',
       ],
       'sources': [
         '../gm/gm_expectations.h',
         '../gm/gm_expectations.cpp',
       ],
       'dependencies': [
         'skia_lib.gyp:skia_lib',
+        'flags.gyp:flags',
         'jsoncpp.gyp:jsoncpp',
       ],
       'direct_dependent_settings': {
         'include_dirs': [
           '../gm/',
         ],
       },
     },
     {
       'target_name': 'gm',
@@ skipping 72 matching lines @@
       ],
     },
   ],
 }
 
 # Local Variables:
 # tab-width:2
 # indent-tabs-mode:nil
 # End:
 # vim: set expandtab tabstop=2 shiftwidth=2: