Add string art GM and sample.

gyp/SampleApp.gyp

 {
   'variables': {
     #manually set sample_pdf_file_viewer to 1 to have the PdfViewer in SampleApp
     'sample_pdf_file_viewer%': 0,
   },
   'targets': [
     {
       'target_name': 'SampleApp',
       'type': 'executable',
       'mac_bundle' : 1,
@@ skipping 84 matching lines @@
         '../samplecode/SamplePictFile.cpp',
         '../samplecode/SamplePoints.cpp',
         '../samplecode/SamplePolyToPoly.cpp',
         '../samplecode/SampleRegion.cpp',
         '../samplecode/SampleRepeatTile.cpp',
         '../samplecode/SampleRotateCircles.cpp',
         '../samplecode/SampleShaders.cpp',
         '../samplecode/SampleShaderText.cpp',
         '../samplecode/SampleSkLayer.cpp',
         '../samplecode/SampleSlides.cpp',
+        '../samplecode/SampleStringArt.cpp',
         '../samplecode/SampleStrokePath.cpp',
         '../samplecode/SampleTests.cpp',
         '../samplecode/SampleText.cpp',
         '../samplecode/SampleTextAlpha.cpp',
         '../samplecode/SampleTextBox.cpp',
         '../samplecode/SampleTextOnPath.cpp',
         '../samplecode/SampleTextureDomain.cpp',
         '../samplecode/SampleTiling.cpp',
         '../samplecode/SampleTinyBitmap.cpp',
         '../samplecode/SampleUnitMapper.cpp',
@@ skipping 202 matching lines @@
       },
     },
   ],
 }
 
 # Local Variables:
 # tab-width:2
 # indent-tabs-mode:nil
 # End:
 # vim: set expandtab tabstop=2 shiftwidth=2: