Check libpng directly into third_party/

gyp/libpng.gyp

 # Copyright 2014 Google Inc.
 #
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 {
   'variables': {
     'skia_warnings_as_errors': 0,
   },
   'targets': [
     {
       'target_name': 'libpng',
       'type': 'none',
       'conditions': [
         [ 'skia_android_framework', {
             'dependencies':              [ 'android_deps.gyp:png' ],
             'export_dependent_settings': [ 'android_deps.gyp:png' ],
         },{
             'dependencies':              [ 'libpng.gyp:libpng_static' ],
             'export_dependent_settings': [ 'libpng.gyp:libpng_static' ],
         }]
       ]
     },
     {
       'target_name': 'libpng_static',
       'type': 'static_library',
       'standalone_static_library': 1,
       'include_dirs': [
-        # Needed for generated pnglibconf.h and pngprefix.h
         '../third_party/libpng',
-        '../third_party/externals/libpng',
       ],
       'dependencies': [
         'zlib.gyp:zlib',
       ],
       'export_dependent_settings': [
         'zlib.gyp:zlib',
       ],
       'direct_dependent_settings': {
         'include_dirs': [
-          '../third_party/externals/libpng',
-          # Needed for generated pnglibconf.h and pngprefix.h
           '../third_party/libpng',
         ],
       },
       'cflags': [
         '-w',
         '-fvisibility=hidden',
       ],
       'sources': [
-        '../third_party/externals/libpng/png.c',
-        '../third_party/externals/libpng/pngerror.c',
-        '../third_party/externals/libpng/pngget.c',
-        '../third_party/externals/libpng/pngmem.c',
-        '../third_party/externals/libpng/pngpread.c',
-        '../third_party/externals/libpng/pngread.c',
-        '../third_party/externals/libpng/pngrio.c',
-        '../third_party/externals/libpng/pngrtran.c',
-        '../third_party/externals/libpng/pngrutil.c',
-        '../third_party/externals/libpng/pngset.c',
-        '../third_party/externals/libpng/pngtrans.c',
-        '../third_party/externals/libpng/pngwio.c',
-        '../third_party/externals/libpng/pngwrite.c',
-        '../third_party/externals/libpng/pngwtran.c',
-        '../third_party/externals/libpng/pngwutil.c',
+        '../third_party/libpng/png.c',
+        '../third_party/libpng/pngerror.c',
+        '../third_party/libpng/pngget.c',
+        '../third_party/libpng/pngmem.c',
+        '../third_party/libpng/pngpread.c',
+        '../third_party/libpng/pngread.c',
+        '../third_party/libpng/pngrio.c',
+        '../third_party/libpng/pngrtran.c',
+        '../third_party/libpng/pngrutil.c',
+        '../third_party/libpng/pngset.c',
+        '../third_party/libpng/pngtrans.c',
+        '../third_party/libpng/pngwio.c',
+        '../third_party/libpng/pngwrite.c',
+        '../third_party/libpng/pngwtran.c',
+        '../third_party/libpng/pngwutil.c',
       ],
       'conditions': [
         [ '"x86" in skia_arch_type', {
           'defines': [
             'PNG_INTEL_SSE_OPT=1',
           ],
           'sources': [
-            '../third_party/externals/libpng/contrib/intel/intel_init.c',
-            '../third_party/externals/libpng/contrib/intel/filter_sse2_intrinsics.c',
+            '../third_party/libpng/contrib/intel/intel_init.c',
+            '../third_party/libpng/contrib/intel/filter_sse2_intrinsics.c',
           ],
         }],
         [ '(("arm64" == skia_arch_type) or                   \
             ("arm" == skia_arch_type and arm_neon == 1)) and \
            ("ios" != skia_os)', {
           'defines': [
             'PNG_ARM_NEON_OPT=2',
             'PNG_ARM_NEON_IMPLEMENTATION=1',
           ],
           'sources': [
-            '../third_party/externals/libpng/arm/arm_init.c',
-            '../third_party/externals/libpng/arm/filter_neon_intrinsics.c',
+            '../third_party/libpng/arm/arm_init.c',
+            '../third_party/libpng/arm/filter_neon_intrinsics.c',
           ],
         }],
         [ '"ios" == skia_os', {
           'defines': [
             'PNG_ARM_NEON_OPT=0',
           ],
         }],
       ],
     }
   ]
 }