Add support for building "ios_chrome_unittests" with gn.

ios/web/js_compile.gni

 # Copyright 2015 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.
 
 import("//build/util/java_action.gni")
 
 declare_args() {
   # Control whether the JavaScript files shipped with Chrome on iOS are
   # compiled with closure_compiler or not. Useful for debugging.
   compile_javascript = true
@@ skipping 12 matching lines @@
 #
 #   deps (optional)
 #     List of targets required by this target.
 #
 #   visibility (optional)
 #     Visibility restrictions.
 #
 # Generates a single JavaScript bundle file that can be put in the application
 # bundle.
 #
-# TODO(eugenebut): this should uses the same error flags as js_compile_checked.
+# TODO(crbug.com/487804): once all errors have been fixed, sync with the flags
+# from third_party/closure_compiler/closure_args.gni.
 template("js_compile_bundle") {
   assert(defined(invoker.sources),
          "Need sources in $target_name listing the js files.")
 
   assert(defined(invoker.closure_entry_point),
          "Need closure_entry_point in $target_name for generated js file.")
 
   java_action(target_name) {
     forward_variables_from(invoker,
                            [
@@ skipping 35 matching lines @@
 # Variables
 #   sources:
 #     List of JavaScript files to compile.
 #
 #   deps (optional)
 #     List of targets required by this target.
 #
 #   visibility (optional)
 #     Visibility restrictions.
 #
-# TODO(eugenebut): use flags from third_party/closure_compiler/closure_args.gni
-# once they are the same.
+# TODO(crbug.com/487804): once all errors have been fixed, sync with the flags
+# from third_party/closure_compiler/closure_args.gni.
 template("js_compile_checked") {
   assert(defined(invoker.sources),
          "Need sources in $target_name listing the js files.")
 
   if (compile_javascript) {
     java_action_foreach(target_name) {
       forward_variables_from(invoker,
                              [
                                "deps",
                                "visibility",
                              ])
 
       script = closure_compiler_path
       sources = invoker.sources
       outputs = [
         "$target_gen_dir/{{source_file_part}}",
       ]
 
-      # TODO(eugenebut): need to enable the following compilation checks once
-      # the corresponding errors have been fixed:
+      # TODO(crbug.com/487804): need to enable the following compilation checks
+      # once the corresponding errors have been fixed:
       #   --jscomp_error=checkTypes
       #   --jscomp_error=checkVars
       #   --jscomp_error=missingProperties
       #   --jscomp_error=missingReturn
       #   --jscomp_error=undefinedVars
 
       args = [
         "--compilation_level",
         "SIMPLE_OPTIMIZATIONS",
         "--jscomp_error=accessControls",
@@ skipping 41 matching lines @@
       # to move in the application bundle, equivalent to the following gyp code:
       #
       # "link_settings": {
       #   "mac_bundle_resources": [
       #     "<(SHARED_INTERMEDIATE_DIR)/<(RULE_INPUT_NAME).js",
       #   ],
       # },
     }
   }
 }
+
+# Defines a target that compile JavaScript files without error checking using
+# the closure compiler.
+#
+# Variables
+#   sources:
+#     List of JavaScript files to compile.
+#
+#   deps (optional)
+#     List of targets required by this target.
+#
+#   visibility (optional)
+#     Visibility restrictions.
+#
+# TODO(crbug.com/487804): once all errors have been fixed, remove this template
+# and port all code to use js_compile_checked instead.
+template("js_compile_unchecked") {
+  assert(defined(invoker.sources),
+         "Need sources in $target_name listing the js files.")
+
+  if (compile_javascript) {
+    java_action_foreach(target_name) {
+      forward_variables_from(invoker,
+                             [
+                               "deps",
+                               "visibility",
+                             ])
+
+      script = closure_compiler_path
+      sources = invoker.sources
+      outputs = [
+        "$target_gen_dir/{{source_file_part}}",
+      ]
+
+      args = [
+        "--compilation_level",
+        "SIMPLE_OPTIMIZATIONS",
+        "--js",
+        "{{source}}",
+        "--js_output_file",
+        rebase_path("$target_gen_dir/{{source_file_part}}", root_build_dir),
+      ]
+
+      # TODO(crbug.com/546283): add the generated bundle to the list of files
+      # to move in the application bundle, equivalent to the following gyp code:
+      #
+      # "link_settings": {
+      #   "mac_bundle_resources": [
+      #     "<(SHARED_INTERMEDIATE_DIR)/<(RULE_INPUT_NAME).js",
+      #   ],
+      # },
+    }
+  } else {
+    copy(target_name) {
+      forward_variables_from(invoker,
+                             [
+                               "deps",
+                               "visibility",
+                             ])
+
+      sources = invoker.sources
+      outputs = [
+        "$target_gen_dir/{{source_file_part}}",
+      ]
+
+      # TODO(crbug.com/546283): add the generated bundle to the list of files
+      # to move in the application bundle, equivalent to the following gyp code:
+      #
+      # "link_settings": {
+      #   "mac_bundle_resources": [
+      #     "<(SHARED_INTERMEDIATE_DIR)/<(RULE_INPUT_NAME).js",
+      #   ],
+      # },
+    }
+  }
+}