Enable unused param checking for public includes.

gyp/tools.gyp

 # GYP file to build various tools.
 #
 # To build on Linux:
 #  ./gyp_skia tools.gyp && make tools
 #
 {
   'includes': [
     'apptype_console.gypi',
   ],
   'targets': [
@@ skipping 610 matching lines @@
         '../tools/ProcStats.h',
         '../tools/ProcStats.cpp',
       ],
       'direct_dependent_settings': {
         'include_dirs': [ '../tools', ],
       },
     },
     {
       'target_name': 'test_public_includes',
       'type': 'static_library',
-      #'cflags!': [ '-Wno-unused-parameter' ],
+      # Ensure that our public headers don't have unused params so that clients
+      # (e.g. Android) that include us can build with these warnings enabled
+      'cflags!': [ '-Wno-unused-parameter' ],
       'variables': {
         'includes_to_test': [
           '<(skia_include_path)/animator',
           '<(skia_include_path)/c',
           '<(skia_include_path)/config',
           '<(skia_include_path)/core',
           '<(skia_include_path)/effects',
           '<(skia_include_path)/gpu',
           '<(skia_include_path)/images',
           '<(skia_include_path)/pathops',
@@ skipping 135 matching lines @@
               'flags.gyp:flags',
               'skia_lib.gyp:skia_lib',
               'resources',
             ],
           },
         ],
       },
     ],
   ],
 }