Build ZIP archiver in ui/file_manager.

ui/file_manager/zip_archiver/BUILD.gn

+# Copyright 2017 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/config/features.gni")
+
+if (enable_nacl) {
+  copy("zip_archiver") {
+    pexe_dir = get_label_info(
+        "//ui/file_manager/zip_archiver/zip_archiver/cpp:zip_archiver_pnacl(//build/toolchain/nacl:newlib_pnacl)",
+        "root_out_dir")
+
+    sources = [
+      "$pexe_dir/zip_archiver_pnacl.pexe",
+    ]
+
+    outputs = [
+      "$pexe_dir/../gen/ui/file_manager/{{source_file_part}}.js",

[hashimoto, 2017/04/12 07:59:43]

1. Why do we need to copy this file once, instead of directly referencing the
pexe file in ui/file_manager/BUILD.gn? 
2. Can't we avoid using "../" in the path?
3. Why is the extension ".js"?

[takise, 2017/04/12 09:30:00]

This is actually a really tricky workaround which ImageLoader already uses to
load NaCL module.
Basically, .grd file can not read files that end with .pexe or .nmf. 

https://cs.chromium.org/chromium/src/ui/file_manager/image_loader/piex_loader...

NaCL toolchain in GN automatically create .pexe file, so we need to change the
file extension here. 
I tried to use .pexe.txt instead of .pexe before, but it didn't work. That's why
I'm using .pexe.js here.

I investigated this issue for a few days before, but I couldn't find out why
.pexe and .nmf don't work, so now I just followed the same way as ImageLoader.
Done.

+    ]
+
+    deps = [
+      "//ui/file_manager/zip_archiver/cpp:zip_archiver_pnacl",
+    ]
+  }
+}