add sample to exercise hittesting

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',
@@ skipping 54 matching lines @@
         '../samplecode/SampleFilter.cpp',
         '../samplecode/SampleFilter2.cpp',
         '../samplecode/SampleFilterFuzz.cpp',
         '../samplecode/SampleFontCache.cpp',
         '../samplecode/SampleFontScalerTest.cpp',
         '../samplecode/SampleFuzz.cpp',
         '../samplecode/SampleGradients.cpp',
         '../samplecode/SampleHairCurves.cpp',
         '../samplecode/SampleHairline.cpp',
         '../samplecode/SampleHairModes.cpp',
+        '../samplecode/SampleHT.cpp',
         '../samplecode/SampleIdentityScale.cpp',
         '../samplecode/SampleLayerMask.cpp',
         '../samplecode/SampleLayers.cpp',
         '../samplecode/SampleLCD.cpp',
         '../samplecode/SampleLines.cpp',
         '../samplecode/SampleLua.cpp',
         '../samplecode/SampleManyRects.cpp',
         '../samplecode/SampleMeasure.cpp',
         '../samplecode/SampleMipMap.cpp',
         '../samplecode/SampleMovie.cpp',
@@ skipping 217 matching lines @@
         }],
       ],
       'msvs_settings': {
         'VCLinkerTool': {
           'SubSystem': '2',
         },
       },
     },
   ],
 }