Add a BUILD target and a script to build a public static library for ios/web_view.

ios/web_view/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.
 
 # Public target that should be used to depend on web_view. Only give access
 # to the web_view public headers while still linking with the implementation.
 group("web_view") {
   public_deps = [
     "//ios/web_view/public",
   ]
   deps = [
     "//ios/web_view/internal",
   ]
 }
+
+# Build and use this .a file to use this library in apps outside Chromium
+# code base. This is a complete static library (containing all dependencies),
+# and it doesn't expose internal symbols to reduce risk of symbol conflict.
+copy("lib_web_view") {
+  deps = [
+    "//ios/web_view/internal:lib_web_view",
+  ]
+  sources = [
+    "$target_out_dir/internal/libweb_view.a",
+  ]
+  outputs = [
+    "$target_out_dir/libweb_view.a",
+  ]
+}