Add JSON output option to bench.

gyp/bench.gyp

 # GYP file to build performance testbench.
 #
 {
   'includes': [
     'apptype_console.gypi',
   ],
   'targets': [
     {
       'target_name': 'bench',
       'type': 'executable',
       'include_dirs' : [
         '../src/core',
         '../src/effects',
         '../src/utils',
       ],
       'includes': [
         'bench.gypi'
       ],
       'dependencies': [
         'skia_lib.gyp:skia_lib',
         'bench_timer',
         'flags.gyp:flags',
+        'jsoncpp.gyp:jsoncpp',
       ],
       'conditions': [
         ['skia_gpu == 1',
           {
             'include_dirs' : [
               '../src/gpu',
             ],
           },
         ],
       ],
@@ skipping 53 matching lines @@
       ],
     }
   ],
 }
 
 # Local Variables:
 # tab-width:2
 # indent-tabs-mode:nil
 # End:
 # vim: set expandtab tabstop=2 shiftwidth=2: