Separate and update PDF_DIFF_TRACE_IN_PNG

gyp/pdfviewer_lib.gyp

 # GYP file to build pdfviewer.
 #
 # To build on Linux:
 #  ./gyp_skia pdfviewer.gyp && make pdfviewer
 #
 {
   'targets': [
     {
       'target_name': 'pdfviewer_lib',
       'type': 'static_library',
       'sources': [
         # FIXME: Include directory is named "inc" (instead of "include") in
         # order to not be considered the public API.
         '../experimental/PdfViewer/inc/SkPdfContext.h',
+        '../experimental/PdfViewer/inc/SkPdfDiffEncoder.h',
         '../experimental/PdfViewer/inc/SkPdfRenderer.h',
         '../experimental/PdfViewer/inc/SkPdfTokenLooper.h',
 
         '../experimental/PdfViewer/src/SkPdfContext.cpp',
         '../experimental/PdfViewer/src/SkPdfRenderer.cpp',
         '../experimental/PdfViewer/src/SkTDStackNester.h',
-        '../experimental/PdfViewer/src/SkPdfTokenLooper.cpp',
+        '../experimental/PdfViewer/src/SkPdfDiffEncoder.cpp',
 
         '../experimental/PdfViewer/SkPdfGraphicsState.cpp',
         '../experimental/PdfViewer/SkPdfFont.cpp',
         '../experimental/PdfViewer/SkPdfReporter.cpp',
         '../experimental/PdfViewer/SkPdfUtils.cpp',
         #'../experimental/PdfViewer/SkPdfNYI.cpp',
         '../experimental/PdfViewer/SkTrackDevice.cpp',
         '../experimental/PdfViewer/SkTracker.cpp',
         '../experimental/PdfViewer/pdfparser/native/SkPdfNativeObject.cpp',
         '../experimental/PdfViewer/pdfparser/native/SkPdfNativeTokenizer.cpp',
@@ skipping 15 matching lines @@
       ],
     },
   ],
 }
 
 # Local Variables:
 # tab-width:2
 # indent-tabs-mode:nil
 # End:
 # vim: set expandtab tabstop=2 shiftwidth=2: