Don't require getLength on Mac.

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 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',
@@ skipping 134 matching lines @@
       },
     },
   ],
 }
 
 # Local Variables:
 # tab-width:2
 # indent-tabs-mode:nil
 # End:
 # vim: set expandtab tabstop=2 shiftwidth=2: