Remove ImageDataFetcher from iOS.

ios/web/public/image_fetcher/BUILD.gn

 # Copyright 2016 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("image_fetcher") {
   configs += [ "//build/config/compiler:enable_arc" ]
   sources = [
-    "image_data_fetcher.h",
-    "image_data_fetcher.mm",
     "webp_decoder.h",
     "webp_decoder.mm",
   ]
   deps = [
     "//base",
-    "//net",
     "//third_party/libwebp:libwebp_dec",
   ]
 }
 
 source_set("unit_tests") {
   configs += [ "//build/config/compiler:enable_arc" ]
   testonly = true
   sources = [
-    "image_data_fetcher_unittest.mm",
     "webp_decoder_unittest.mm",
   ]
   deps = [
     ":image_fetcher",
     ":webp_transcode_unit_tests_bundle_data",
     "//base",
-    "//net",
-    "//net:test_support",
     "//testing/gmock",
     "//testing/gtest",
   ]
   libs = [ "CoreGraphics.framework" ]
 }
 
 bundle_data("webp_transcode_unit_tests_bundle_data") {
   visibility = [ ":unit_tests" ]
   testonly = true
   sources = [
     "//ios/web/test/data/webp_transcode/test.jpg",
     "//ios/web/test/data/webp_transcode/test.webp",
     "//ios/web/test/data/webp_transcode/test_alpha.png",
     "//ios/web/test/data/webp_transcode/test_alpha.webp",
     "//ios/web/test/data/webp_transcode/test_small.tiff",
     "//ios/web/test/data/webp_transcode/test_small.webp",
   ]
   outputs = [
     "{{bundle_resources_dir}}/{{source_root_relative_dir}}/" +
         "{{source_file_part}}",
   ]
 }