Remove unused (by clients) SkUnitMapper (https://codereview.chromium.org/283273002/)

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 88 matching lines @@
         '../samplecode/SampleSlides.cpp',
         '../samplecode/SampleStringArt.cpp',
         '../samplecode/SampleStrokePath.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',
         '../samplecode/SampleUnpremul.cpp',
         '../samplecode/SampleVertices.cpp',
         '../samplecode/SampleXfermodesBlur.cpp',
         '../samplecode/TransitionView.cpp',
         '../samplecode/TransitionView.h',
 
         # DrawingBoard
         #'../experimental/DrawingBoard/SkColorPalette.h',
         #'../experimental/DrawingBoard/SkColorPalette.cpp',
         #'../experimental/DrawingBoard/SkNetPipeController.h',
@@ skipping 146 matching lines @@
           },
           'xcode_config_file': '../experimental/iOSSampleApp/SkiOSSampleApp-Base.xcconfig',
           'mac_bundle_resources' : [
             '../experimental/iOSSampleApp/iPad/MainWindow_iPad.xib',
             '../experimental/iOSSampleApp/iPhone/MainWindow_iPhone.xib',
           ],
         }],
         [ 'skia_os == "android"', {
           'sources!': [
             '../samplecode/SampleAnimator.cpp',
-            '../samplecode/SampleUnitMapper.cpp',
           ],
           'dependencies!': [
             'animator.gyp:animator',
             'experimental.gyp:experimental',
           ],
           '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',
         },
       },
     },
   ],
 }