Move WebpDecoder from ios/web to components/image_fetcher

ios/web/BUILD.gn

Index: ios/web/BUILD.gn
diff --git a/ios/web/BUILD.gn b/ios/web/BUILD.gn
index 5a84a02fca620aa990328f66bd9b8b08543fe557..8b6883c0818f868c2d6d94d09a79f00af7473108 100644
--- a/ios/web/BUILD.gn
+++ b/ios/web/BUILD.gn
@@ -263,7 +263,6 @@ source_set("web") {
     "//components/url_formatter",
     "//ios/net",
     "//ios/third_party/blink:html_tokenizer",
-    "//ios/web/public/image_fetcher",
     "//mojo/public/cpp/system",
     "//mojo/public/js",
     "//net",
@@ -380,7 +379,6 @@ source_set("test_support") {
     "//ios/testing:ios_test_support",
     "//ios/testing:ocmock_support",
     "//ios/third_party/gcdwebserver",
-    "//ios/web/public/image_fetcher",
     "//ios/web/test:mojo_bindings",
     "//net:test_support",
     "//testing/gmock",
@@ -511,7 +509,6 @@ test("ios_web_unittests") {
     "//components/url_formatter",
     "//ios/net",
     "//ios/testing:ocmock_support",
-    "//ios/web/public/image_fetcher:unit_tests",
     "//ios/web/test:mojo_bindings",
     "//net:test_support",
     "//services/service_manager/public/cpp",