Add basic stacktrace handler using libunwind.

gyp/bench.gyp

 # GYP file to build performance testbench.
 #
 {
   'includes': [
     'apptype_console.gypi',
   ],
   'targets': [
     {
       'target_name': 'bench',
       'type': 'executable',
       'dependencies': [
-        'skia_lib.gyp:skia_lib',
         'bench_timer',
+        'crash_handler.gyp:CrashHandler',
+        'etc1.gyp:libetc1',
         'flags.gyp:flags',
         'jsoncpp.gyp:jsoncpp',
-        'etc1.gyp:libetc1',
+        'skia_lib.gyp:skia_lib',
       ],
       'sources': [
         '../bench/ResultsWriter.cpp',
         '../bench/SkBenchLogger.cpp',
         '../bench/SkBenchLogger.h',
         '../bench/SkGMBench.cpp',
         '../bench/SkGMBench.h',
         '../bench/benchmain.cpp',
         '../tools/sk_tool_utils.cpp',
       ],
@@ skipping 74 matching lines @@
         ['skia_gpu == 1', {
           'sources': [
             '../bench/BenchGpuTimer_gl.h',
             '../bench/BenchGpuTimer_gl.cpp',
           ],
         }],
       ],
     }
   ],
 }