add interactive xfer sample

gyp/SampleApp.gyp

 # Copyright 2015 Google Inc.
 #
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 #
 {
   'includes': [
     'apptype_console.gypi',
   ],
   'targets': [
@@ skipping 101 matching lines @@
         '../samplecode/SampleText.cpp',
         '../samplecode/SampleTextAlpha.cpp',
         '../samplecode/SampleTextBox.cpp',
         '../samplecode/SampleTextOnPath.cpp',
         '../samplecode/SampleTextureDomain.cpp',
         '../samplecode/SampleTiling.cpp',
         '../samplecode/SampleTinyBitmap.cpp',
         '../samplecode/SampleUnpremul.cpp',
         '../samplecode/SampleVertices.cpp',
         '../samplecode/SampleXfermodesBlur.cpp',
+        '../samplecode/SampleXfer.cpp',
 
         # DrawingBoard
         #'../experimental/DrawingBoard/SkColorPalette.h',
         #'../experimental/DrawingBoard/SkColorPalette.cpp',
         #'../experimental/DrawingBoard/SkNetPipeController.h',
         #'../experimental/DrawingBoard/SkNetPipeController.cpp',
         #'../experimental/DrawingBoard/SampleDrawingClient.cpp',
         #'../experimental/DrawingBoard/SampleDrawingServer.cpp',
 
         # Networking
@@ skipping 124 matching lines @@
           ],
         }],
         [ 'not skia_pdf', {
           'dependencies!': [ 'pdf.gyp:pdf' ],
           'dependencies': [ 'pdf.gyp:nopdf' ],
         }],
       ],
     },
   ],
 }