Use the upstream version of libwebp, v0.4.3.

gyp/libwebp.gyp

Index: gyp/libwebp.gyp
diff --git a/gyp/libwebp.gyp b/gyp/libwebp.gyp
index 70fffdd925251c8c8fc7a2338c8c5e2898326850..4635df3f5873ed1bba442362ed7c07b6b2fa1022 100644
--- a/gyp/libwebp.gyp
+++ b/gyp/libwebp.gyp
@@ -28,7 +28,6 @@
             '../third_party/externals/libwebp/src/dec/frame.c',
             '../third_party/externals/libwebp/src/dec/idec.c',
             '../third_party/externals/libwebp/src/dec/io.c',
-            '../third_party/externals/libwebp/src/dec/layer.c',
             '../third_party/externals/libwebp/src/dec/quant.c',
             '../third_party/externals/libwebp/src/dec/tree.c',
             '../third_party/externals/libwebp/src/dec/vp8.c',
@@ -57,15 +56,20 @@
               '../third_party/externals/libwebp',
           ],
           'sources': [
+            '../third_party/externals/libwebp/src/dsp/alpha_processing.c',
+            '../third_party/externals/libwebp/src/dsp/alpha_processing_sse2.c',
             '../third_party/externals/libwebp/src/dsp/cpu.c',
             '../third_party/externals/libwebp/src/dsp/dec.c',
+            '../third_party/externals/libwebp/src/dsp/dec_clip_tables.c',
             '../third_party/externals/libwebp/src/dsp/dec_sse2.c',
             '../third_party/externals/libwebp/src/dsp/enc.c',
             '../third_party/externals/libwebp/src/dsp/enc_sse2.c',
             '../third_party/externals/libwebp/src/dsp/lossless.c',
+            '../third_party/externals/libwebp/src/dsp/lossless_sse2.c',
             '../third_party/externals/libwebp/src/dsp/upsampling.c',
             '../third_party/externals/libwebp/src/dsp/upsampling_sse2.c',
             '../third_party/externals/libwebp/src/dsp/yuv.c',
+            '../third_party/externals/libwebp/src/dsp/yuv_sse2.c',
           ],
           'cflags': [ '-w' ],
           'xcode_settings': { 'WARNING_CFLAGS': [ '-w' ] },
@@ -116,8 +120,8 @@
             '../third_party/externals/libwebp/src/enc/frame.c',
             '../third_party/externals/libwebp/src/enc/histogram.c',
             '../third_party/externals/libwebp/src/enc/iterator.c',
-            '../third_party/externals/libwebp/src/enc/layer.c',
             '../third_party/externals/libwebp/src/enc/picture.c',
+            '../third_party/externals/libwebp/src/enc/picture_csp.c',
             '../third_party/externals/libwebp/src/enc/quant.c',
             '../third_party/externals/libwebp/src/enc/syntax.c',
             '../third_party/externals/libwebp/src/enc/token.c',
@@ -143,6 +147,7 @@
             '../third_party/externals/libwebp/src/utils/huffman_encode.c',
             '../third_party/externals/libwebp/src/utils/quant_levels.c',
             '../third_party/externals/libwebp/src/utils/quant_levels_dec.c',
+            '../third_party/externals/libwebp/src/utils/random.c',
             '../third_party/externals/libwebp/src/utils/rescaler.c',
             '../third_party/externals/libwebp/src/utils/thread.c',
             '../third_party/externals/libwebp/src/utils/utils.c',
@@ -174,7 +179,7 @@
         },
       ],
     }, {
-      # use_system_libwep == 1
+      # use_system_libwebp == 1
       'targets': [
         {
           'target_name': 'libwebp',