Add SkImageGenerator Interface

gyp/images.gyp

 # GYP file for images project.
 {
   'targets': [
     {
       'target_name': 'images',
       'product_name': 'skia_images',
       'type': 'static_library',
       'standalone_static_library': 1,
       'dependencies': [
         'core.gyp:*',
         'libjpeg.gyp:*',
         'libwebp.gyp:libwebp',
         'utils.gyp:utils',
       ],
       'export_dependent_settings': [
         'libjpeg.gyp:*',
       ],
       'include_dirs': [
         '../include/images',
         '../include/lazy',
+        # for access to SkDiscardablePixelRef.h
+        '../src/lazy',
         # for access to SkErrorInternals.h
         '../src/core/',
         # for access to SkImagePriv.h
         '../src/image/',
         # So src/ports/SkImageDecoder_CG can access SkStreamHelpers.h
         '../src/images/',
       ],
       'sources': [
         '../include/images/SkForceLinking.h',
         '../include/images/SkImageRef.h',
         '../include/images/SkImageRef_GlobalPool.h',
         '../src/images/SkJpegUtility.h',
         '../include/images/SkMovie.h',
         '../include/images/SkPageFlipper.h',
 
         '../src/images/bmpdecoderhelper.cpp',
         '../src/images/bmpdecoderhelper.h',
 
         '../src/images/SkForceLinking.cpp',
         '../src/images/SkImageDecoder.cpp',
+        '../src/images/SkDecodingImageGenerator.cpp',
         '../src/images/SkImageDecoder_FactoryDefault.cpp',
         '../src/images/SkImageDecoder_FactoryRegistrar.cpp',
         # If decoders are added/removed to/from (all/individual)
         # platform(s), be sure to update SkForceLinking.cpp
         # so the right decoders will be forced to link.
         '../src/images/SkImageDecoder_libbmp.cpp',
         '../src/images/SkImageDecoder_libgif.cpp',
         '../src/images/SkImageDecoder_libico.cpp',
         '../src/images/SkImageDecoder_libjpeg.cpp',
         '../src/images/SkImageDecoder_libpng.cpp',
@@ skipping 120 matching lines @@
       },
     },
   ],
 }
 
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