Fix missing headers in libwebp

components/image_fetcher/ios/BUILD.gn

 # Copyright 2017 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 source_set("ios") {
   sources = [
     "ios_image_data_fetcher_wrapper.h",
     "ios_image_data_fetcher_wrapper.mm",
     "ios_image_decoder_impl.h",
     "ios_image_decoder_impl.mm",
     "webp_decoder.h",
     "webp_decoder.mm",
   ]
   deps = [
     "//base",
     "//components/image_fetcher/core",
     "//ios/web",
     "//net",
     "//third_party/libwebp:libwebp_dec",
+    "//third_party/libwebp:libwebp_webp",
     "//ui/gfx",
   ]
   configs += [ "//build/config/compiler:enable_arc" ]
 }
 
 source_set("unit_tests") {
   testonly = true
   sources = [
     "ios_image_data_fetcher_wrapper_unittest.mm",
     "ios_image_decoder_impl_unittest.mm",
@@ skipping 21 matching lines @@
     "//components/test/data/webp_transcode/test_alpha.png",
     "//components/test/data/webp_transcode/test_alpha.webp",
     "//components/test/data/webp_transcode/test_small.tiff",
     "//components/test/data/webp_transcode/test_small.webp",
   ]
   outputs = [
     "{{bundle_resources_dir}}/{{source_root_relative_dir}}/" +
         "{{source_file_part}}",
   ]
 }