Remove all code related to NaCl

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.
 #
 {
   'variables': {
     #manually set sample_pdf_file_viewer to 1 to have the PdfViewer in SampleApp
     'sample_pdf_file_viewer%': 0,
   },
@@ skipping 279 matching lines @@
           ],
           'dependencies': [
             'android_deps.gyp:Android_SampleApp',
           ],
         }],
         [ 'skia_gpu == 1', {
           'dependencies': [
             'gputest.gyp:skgputest',
           ],
         }],
-        [ 'skia_os == "nacl"', {
-          'sources': [
-            '../../nacl/src/nacl_sample.cpp',
-          ],
-        }],
       ],
       'msvs_settings': {
         'VCLinkerTool': {
           'SubSystem': '2',
         },
       },
     },
   ],
 }