Add missing .h files to .gn files that have a .cc file next to it in the gn file already.

third_party/WebKit/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("//build/buildflag_header.gni")
 import("//mojo/public/tools/bindings/mojom.gni")
 import("//third_party/WebKit/public/public_features.gni")
 import("//third_party/WebKit/Source/config.gni")
 import("//third_party/WebKit/Source/core/core.gni")
 import("//tools/grit/grit_rule.gni")
@@ skipping 740 matching lines @@
   ]
 }
 
 # Some mojom typemaps are shared between Chromium and Blink variants and
 # therefore require some shared traits implementation. These definitions are
 # relegated to a separate target to avoid duplication between the variants.
 source_set("shared_typemap_traits") {
   visibility = [ ":*" ]
   sources = [
     "web/ConsoleMessageStructTraits.cpp",
+    "web/ConsoleMessageStructTraits.h",
   ]
   deps = [
     ":mojo_bindings_shared__generator",
   ]
 }