Fix missing headers in WebKit/public:mojo_bindings

mojo/public/tools/bindings/mojom.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.
 
 declare_args() {
   # Indicates whether typemapping should be supported in this build
   # configuration. This may be disabled when building external projects which
   # depend on //mojo but which do not need/want all of the Chromium tree
   # dependencies that come with typemapping.
   #
@@ skipping 584 matching lines @@
         if (defined(_typemap_config.sources)) {
           sources += _typemap_config.sources
         }
         if (defined(_typemap_config.public_deps)) {
           public_deps += _typemap_config.public_deps
         }
         if (defined(_typemap_config.deps)) {
           deps += _typemap_config.deps
         }
       }
+      if (defined(invoker.export_header)) {
+        sources += [ "//" + invoker.export_header ]
+      }
       if (defined(bindings_configuration.for_blink) &&
           bindings_configuration.for_blink) {
         public_deps += [ "//mojo/public/cpp/bindings:wtf_support" ]
       }
     }
 
     if (!cpp_only && is_android) {
       import("//build/config/android/rules.gni")
 
       java_srcjar_target_name = target_name + "_java_sources"
@@ skipping 37 matching lines @@
           full_name = get_label_info(d, "label_no_toolchain")
           deps += [ "${full_name}_java" ]
         }
 
         srcjar_deps = [ ":$java_srcjar_target_name" ]
         run_findbugs_override = false
       }
     }
   }
 }