Fix webaudio's grit dependencies.

public/BUILD.gn

 # 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("//third_party/WebKit/Source/config.gni")
 import("//tools/grit/grit_rule.gni")
 
 if (is_android) {
   import("//build/config/android/rules.gni")
 }
 
 # GYP version: WebKit/public/blink.gyp:blink
 group("blink") {
   deps = [
     ":blink_headers",
@@ skipping 622 matching lines @@
 
 # GYP version: WebKit/public/blink_resources.gyp:blink_resources
 grit("resources") {
   output_dir = "$root_gen_dir/blink/public/resources"
   use_qualified_include = true
   source = "blink_resources.grd"
   outputs = [
     "grit/blink_resources.h",
     "blink_resources.pak",
   ]
+  if (use_concatenated_impulse_responses) {
+    grit_flags = [
+      "-D",
+      "use_concatenated_impulse_responses",
+    ]
+  }
 }
 
 # GYP version: WebKit/public/blink_resources.gyp:blink_image_resources
 grit("image_resources") {
   output_dir = "$root_gen_dir/blink/public/resources"
   use_qualified_include = true
   source = "blink_image_resources.grd"
   outputs = [
     "grit/blink_image_resources.h",
     "blink_image_resources_100_percent.pak",
     "blink_image_resources_200_percent.pak",
   ]
 }