Mojo cpp bindings: add support for validating incoming messages.

mojo/public/cpp/bindings/sync_dispatcher.h

Index: mojo/public/cpp/bindings/sync_dispatcher.h
diff --git a/mojo/public/cpp/bindings/sync_dispatcher.h b/mojo/public/cpp/bindings/sync_dispatcher.h
index 752118023940799d46c3c9e716f81bd9dfd4cbfb..695f4399cd5eadf5caf35625478c5cb5a51fba1f 100644
--- a/mojo/public/cpp/bindings/sync_dispatcher.h
+++ b/mojo/public/cpp/bindings/sync_dispatcher.h
@@ -5,6 +5,8 @@
 #ifndef MOJO_PUBLIC_CPP_BINDINGS_SYNC_DISPATCHER_H_
 #define MOJO_PUBLIC_CPP_BINDINGS_SYNC_DISPATCHER_H_
 
+#include "mojo/public/cpp/bindings/lib/filter_chain.h"
+#include "mojo/public/cpp/bindings/lib/message_header_validator.h"
 #include "mojo/public/cpp/system/core.h"
 
 namespace mojo {
@@ -13,6 +15,8 @@ class MessageReceiver;
 
 // Waits for one message to arrive on the message pipe, and dispatch it to the
 // receiver. Returns true on success, false on failure.
+//
+// NOTE: The message hasn't been validated and may be malformed!
 bool WaitForMessageAndDispatch(MessagePipeHandle handle,
                                mojo::MessageReceiver* receiver);
 
@@ -21,15 +25,21 @@ template<typename Interface> class SyncDispatcher {
   SyncDispatcher(ScopedMessagePipeHandle message_pipe, Interface* sink)
       : message_pipe_(message_pipe.Pass()) {
     stub_.set_sink(sink);
+
+    filters_.Append(new internal::MessageHeaderValidator)
+            .Append(new typename Interface::RequestValidator_);
+    filters_.set_sink(&stub_);
   }
 
   bool WaitAndDispatchOneMessage() {
-    return WaitForMessageAndDispatch(message_pipe_.get(), &stub_);
+    return WaitForMessageAndDispatch(message_pipe_.get(),
+                                     filters_.GetHead());
   }
 
  private:
   ScopedMessagePipeHandle message_pipe_;
   typename Interface::Stub_ stub_;
+  internal::FilterChain filters_;
 };
 
 }  // namespace mojo