Add a GN flag for the Windows multi-dll build.

chrome/version.gni

 # Copyright 2014 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/chrome_build.gni")
+
 # Runs the version processing script over the given template file to produce
 # an output file. This is used for generating various forms of files that
 # incorporate the product name and version.
 #
+# Unlike GYP, this will actually compile the resulting file, so you don't need
+# to add it separately to the sources, just depend on the target.
+#
 # This template automatically includes VERSION, LASTCHANGE, and BRANDING. It
 # automatically uses the template file .
 # GYP parameterizes this template file but all current invocations use this
 # same one. If in the future we need to set it, this should be added as an
 # optional argument.
 #
 # In GYP this is a rule that runs once per ".ver" file. In GN this just
 # processes one file per invocation of the template so you may have to have
 # multiple targets.
 #
@@ skipping 24 matching lines @@
 #     sources = [ "myfile.h.in" ]
 #     output = "$target_gen_dir/myfile.h"
 #     extra_args = ["-e", "FOO=42"]
 #     extra_files = [ "foo/BRANDING" ]
 #   }
 template("process_version") {
   assert(defined(invoker.sources) || defined(invoker.template_file),
          "Either sources or template_file must be defined for $target_name")
   assert(defined(invoker.output), "Output must be defined for $target_name")
 
-  action(target_name) {
-    if (defined(invoker.visibility)) {
-      visibility = invoker.visibility
-    }
+  action_name = target_name + "_action"
+  source_set_name = target_name
+
+  action(action_name) {
+    visibility = [ ":$source_set_name" ]
     script = "//build/util/version.py"
 
     lastchange_path = "//build/util/LASTCHANGE"
     version_path = "//chrome/VERSION"
     if (is_chrome_branded) {
       branding_path = "//chrome/app/theme/google_chrome/BRANDING"
     } else {
       branding_path = "//chrome/app/theme/chromium/BRANDING"
     }
     if (defined(invoker.template_file)) {
@@ skipping 34 matching lines @@
       rebase_path(lastchange_path, root_build_dir),
     ]
     if (defined(invoker.extra_args)) {
       args += invoker.extra_args
     }
     args += [
       rebase_path(template_path, root_build_dir),
       rebase_path(invoker.output, root_build_dir),
     ]
   }
+
+  source_set(source_set_name) {
+    if (defined(invoker.visibility)) {
+      visibility = invoker.visibility
+    }
+    sources = get_target_outputs(":$action_name")
+    deps = [
+      ":$action_name",
+    ]
+  }
 }