GN build: don't use "" for grit input.

build/secondary/tools/grit/grit_rule.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.
 
 # Instantiate grit. This will produce a script target to run grit, and a
 # static library that compiles the .cc files.
 #
 # Parameters
 #
 #   source (required)
@@ skipping 295 matching lines @@
   assert(defined(invoker.source),
          "\"source\" must be defined for the grit template $target_name")
 
   grit_inputs = [ invoker.source ]
 
   if (defined(invoker.resource_ids)) {
     resource_ids = invoker.resource_ids
   } else {
     resource_ids = grit_resource_id_file
   }
-  grit_inputs += [ resource_ids ]  # Script depends on ID file.
+  if (resource_ids != "") {
+    # Script depends on ID file. Don't depend on "" if it's the empty string.

[cjhopman, 2015/05/28 18:40:44]

s/on "" if/on resource_ids if/ ? Sentence is kinda odd as is.

+    grit_inputs += [ resource_ids ]
+  }
 
   if (defined(invoker.output_dir)) {
     output_dir = invoker.output_dir
   } else {
     output_dir = target_gen_dir
   }
 
   if (defined(invoker.output_name)) {
     grit_output_name = invoker.output_name
   } else {
@@ skipping 134 matching lines @@
     if (defined(invoker.configs)) {
       configs += invoker.configs
     }
 
     if (defined(invoker.visibility)) {
       visibility = invoker.visibility
     }
     output_name = grit_output_name
   }
 }