Allow Mojo structs as map keys

mojo/public/tools/bindings/generators/cpp_templates/module.h.tmpl

Index: mojo/public/tools/bindings/generators/cpp_templates/module.h.tmpl
diff --git a/mojo/public/tools/bindings/generators/cpp_templates/module.h.tmpl b/mojo/public/tools/bindings/generators/cpp_templates/module.h.tmpl
index 0300956cebefea06f5f5985ca2810e325d2fcb62..f89d207409f8736ad1a3032d61bd0b920554d314 100644
--- a/mojo/public/tools/bindings/generators/cpp_templates/module.h.tmpl
+++ b/mojo/public/tools/bindings/generators/cpp_templates/module.h.tmpl
@@ -67,8 +67,12 @@ namespace {{variant}} {
 #include "mojo/public/cpp/bindings/array.h"
 #include "mojo/public/cpp/bindings/string.h"
 {%- else %}
+{# hash_util.h includes template specializations that should be present for
+   every use of {Inlined}StructPtr. #}
+#include "mojo/public/cpp/bindings/lib/wtf_hash_util.h"
 #include "mojo/public/cpp/bindings/wtf_array.h"
 #include "mojo/public/cpp/bindings/wtf_map.h"
+#include "third_party/WebKit/Source/wtf/HashFunctions.h"
 #include "third_party/WebKit/Source/wtf/Optional.h"
 #include "third_party/WebKit/Source/wtf/text/WTFString.h"
 {%- endif %}