Strip comments and whitespace from Javascript resources

third_party/closure_compiler/compile_js2.gni

+# 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.
+
+import("//third_party/closure_compiler/closure_args.gni")
+
+closure_compiler_dir = "//third_party/closure_compiler"
+
+template("compile_js2_foreach") {
+  action_foreach(target_name) {
+    sources = invoker.sources
+    script = "$closure_compiler_dir/compile2.py"
+    output_name =
+        "{{source_gen_dir}}/closure_${target_name}/{{source_file_part}}"
+    outputs = [
+      output_name,
+    ]
+    closure_args = common_closure_args
+
+    if (defined(invoker.strip_whitespace) && invoker.strip_whitespace) {
+      closure_args += [ "compilation_level=WHITESPACE_ONLY" ]
+    } else {
+      closure_args +=
+          typecheck_closure_args + [ "compilation_level=SIMPLE_OPTIMIZATIONS" ]
+    }
+
+    args = [
+             "{{source}}",
+             "--out_file",
+             rebase_path("$root_out_dir/$output_name"),
+             "--closure_args",
+           ] + closure_args + default_disabled_closure_args
+    deps = invoker.deps
+  }
+}