New SkRTConf macro SK_CONF_TRY_SET: no complaint on missing configuration

gyp/tests.gyp

 # GYP file to build unit tests.
 {
   'includes': [
     'apptype_console.gypi',
   ],
   'targets': [
     {
       'target_name': 'tests',
       'type': 'executable',
       'include_dirs' : [
@@ skipping 102 matching lines @@
         '../tests/QuickRejectTest.cpp',
         '../tests/RandomTest.cpp',
         '../tests/Reader32Test.cpp',
         '../tests/ReadPixelsTest.cpp',
         '../tests/ReadWriteAlphaTest.cpp',
         '../tests/RefCntTest.cpp',
         '../tests/RefDictTest.cpp',
         '../tests/RegionTest.cpp',
         '../tests/ResourceCacheTest.cpp',
         '../tests/RoundRectTest.cpp',
+        '../tests/RuntimeConfigTest.cpp',
         '../tests/RTreeTest.cpp',
         '../tests/SHA1Test.cpp',
         '../tests/ScalarTest.cpp',
         '../tests/SerializationTest.cpp',
         '../tests/ShaderImageFilterTest.cpp',
         '../tests/ShaderOpacityTest.cpp',
         '../tests/Sk64Test.cpp',
         '../tests/skia_test.cpp',
         '../tests/SortTest.cpp',
         '../tests/SrcOverTest.cpp',
@@ skipping 36 matching lines @@
       ],
     },
   ],
 }
 
 # Local Variables:
 # tab-width:2
 # indent-tabs-mode:nil
 # End:
 # vim: set expandtab tabstop=2 shiftwidth=2: