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

gyp/gmslides.gypi

 # include this gypi to include all the golden master slides.
 {
+  'include_dirs': [
+    '../gm',
+    # include dirs needed by particular GMs
+    '../src/utils/debugger',
+    '../src/images',
+    '../src/lazy',
+  ],
   'sources': [
+    # base class for GMs
+    '../gm/gm.cpp',
+    '../gm/gm.h',
+
     '../gm/aaclip.cpp',
     '../gm/aarectmodes.cpp',
     '../gm/alphagradients.cpp',
     '../gm/androidfallback.cpp',
     '../gm/arcofzorro.cpp',
     '../gm/arithmode.cpp',
     '../gm/beziereffects.cpp',
     '../gm/bicubicfilter.cpp',
     '../gm/bigblurs.cpp',
     '../gm/bigmatrix.cpp',
@@ skipping 135 matching lines @@
     '../gm/twopointradial.cpp',
     '../gm/typeface.cpp',
     '../gm/vertices.cpp',
     '../gm/verttext.cpp',
     '../gm/verttext2.cpp',
     '../gm/verylargebitmap.cpp',
     '../gm/xfermodeimagefilter.cpp',
     '../gm/xfermodes.cpp',
     '../gm/xfermodes2.cpp',
     '../gm/xfermodes3.cpp',
+
+    # Files needed by particular GMs
+    '../src/utils/debugger/SkDrawCommand.h',
+    '../src/utils/debugger/SkDrawCommand.cpp',
+    '../src/utils/debugger/SkDebugCanvas.h',
+    '../src/utils/debugger/SkDebugCanvas.cpp',
+    '../src/utils/debugger/SkObjectParser.h',
+    '../src/utils/debugger/SkObjectParser.cpp',
+
   ],
 }