Add asADash entry point into SkPathEffect to allow extracting Dash info from PathEffects

gyp/tests.gypi

 # Common gypi for unit tests.
 {
   'include_dirs': [
     '../src/core',
     '../src/effects',
     '../src/image',
     '../src/lazy',
     '../src/images',
     '../src/pathops',
     '../src/pdf',
@@ skipping 16 matching lines @@
     'record.gyp:record',
   ],
   'sources': [
     '../tests/Test.cpp',
     '../tests/Test.h',
 
     '../tests/AAClipTest.cpp',
     '../tests/ARGBImageEncoderTest.cpp',
     '../tests/AndroidPaintTest.cpp',
     '../tests/AnnotationTest.cpp',
+    '../tests/AsADashTest.cpp',
     '../tests/AtomicTest.cpp',
     '../tests/BBoxHierarchyTest.cpp',
     '../tests/BitSetTest.cpp',
     '../tests/BitmapCopyTest.cpp',
     '../tests/BitmapGetColorTest.cpp',
     '../tests/BitmapHasherTest.cpp',
     '../tests/BitmapHeapTest.cpp',
     '../tests/BitmapTest.cpp',
     '../tests/BlendTest.cpp',
     '../tests/BlitRowTest.cpp',
@@ skipping 142 matching lines @@
 
     '../tests/PipeTest.cpp',
     '../src/pipe/utils/SamplePipeControllers.cpp',
 
     '../tests/TDStackNesterTest.cpp',
     '../experimental/PdfViewer/src/SkTDStackNester.h',
 
     '../tools/sk_tool_utils.cpp',
   ],
 }