Allow GMs ato be used as benchmarks. Make convex_poly_clip opt in.

gyp/bench.gyp

 # GYP file to build performance testbench.
 #
 {
   'includes': [
     'apptype_console.gypi',
   ],
   'targets': [
     {
       'target_name': 'bench',
       'type': 'executable',
@@ skipping 79 matching lines @@
         '../bench/TileBench.cpp',
         '../bench/VertBench.cpp',
         '../bench/WritePixelsBench.cpp',
         '../bench/WriterBench.cpp',
         '../bench/XfermodeBench.cpp',
 
         '../bench/SkBenchLogger.cpp',
         '../bench/SkBenchLogger.h',
         '../bench/SkBenchmark.cpp',
         '../bench/SkBenchmark.h',
+        '../bench/SkGMBench.cpp',
+        '../bench/SkGMBench.h',
+
         '../bench/benchmain.cpp',
       ],
       'conditions': [
         ['skia_gpu == 1',
           {
             'include_dirs' : [
               '../src/gpu',
             ],
             'dependencies': [
               'gputest.gyp:skgputest',
             ],
           },
         ],
       ],
+      'includes': [
+        'gmslides.gypi',
+      ],
     },
     {
       'target_name' : 'bench_timer',
       'type': 'static_library',
       'sources': [
         '../bench/BenchTimer.h',
         '../bench/BenchTimer.cpp',
         '../bench/BenchSysTimer_mach.h',
         '../bench/BenchSysTimer_mach.cpp',
         '../bench/BenchSysTimer_posix.h',
@@ skipping 37 matching lines @@
         ['skia_gpu == 1', {
           'sources': [
             '../bench/BenchGpuTimer_gl.h',
             '../bench/BenchGpuTimer_gl.cpp',
           ],
         }],
       ],
     }
   ],
 }