Generate GRD file in target_gen_dir

This generates the GRD file in out/Default/gen/front_end with the Chromium file
in out/Default/gen/third_party/devtools-frontend/src/front_end. After
https://crrev.com/c/2844838 is submitted, we can remove the old
outfile and remove the copying into out/Default/gen/devtools.

[email protected],[email protected]

Bug: 1174013
Change-Id: Idd7d992c443fcd84d3df83e461d9b5379f9e2b1b
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2846331
Commit-Queue: Tim van der Lippe <[email protected]>
Reviewed-by: Alex Rudenko <[email protected]>
diff --git a/BUILD.gn b/BUILD.gn
index db202d4..224ec8c 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -225,14 +225,15 @@
   }
 
   response_file_contents = rebase_path(inputs, root_build_dir)
-  outfile = "$root_gen_dir/devtools/devtools_resources.grd"
-  outputs = [ outfile ]
-
-  relative_path_dirs = [
-    "$target_gen_dir/front_end",
-    "front_end",
+  outfile_old = "$root_gen_dir/devtools/devtools_resources.grd"
+  outfile = "$target_gen_dir/front_end/devtools_resources.grd"
+  outputs = [
+    outfile,
+    outfile_old,
   ]
 
+  relative_path_dirs = [ "$target_gen_dir/front_end" ]
+
   args = [
            "--file_list",
            "{{response_file_name}}",
@@ -241,6 +242,8 @@
          [
            "--output",
            rebase_path(outfile, root_build_dir),
+           "--output_old",
+           rebase_path(outfile_old, root_build_dir),
          ]
   if (!is_debug) {
     # Compression is slow, particularly in debug builds, so only compress in