Validate flatbuffers before printing in aos_dump, log_cat, and simulated_event_loop

We had a corrupted flatbuffer being logged, and the error was very poor
when it was being printed.  Let's try to catch this a lot earlier.

Fix 1: log_cat should validate before printing.  That'll prevent us
from wasting time debugging why it is crashing and point the finger a
lot better.

Fix 2: aos_dump should do the same.  That'll save us from nasty crashes
there too and focus attention a lot better.

Fix 3: SimulatedEventLoop sender Send should also validate in debug
mode.  This will avoid too big a performance hit in the fast path, but
will catch corrupted flatbuffers in any simulations we do, or any log
replay that gets done with debug turned on.

This caught a couple of places where we were missing schemas, so add
those in too.

Change-Id: I1873ddd592d33fe4e64210a2e08aa9b937d61ab8
Signed-off-by: Austin Schuh <austin.schuh@bluerivertech.com>
diff --git a/aos/events/simulated_event_loop.cc b/aos/events/simulated_event_loop.cc
index ef34839..51021b6 100644
--- a/aos/events/simulated_event_loop.cc
+++ b/aos/events/simulated_event_loop.cc
@@ -806,6 +806,17 @@
   message->context.queue_index = queue_index;
   message->context.data = message->data(channel()->max_size()) +
                           channel()->max_size() - message->context.size;
+
+  DCHECK(channel()->has_schema())
+      << ": Missing schema for channel "
+      << configuration::StrippedChannelToString(channel());
+  DCHECK(flatbuffers::Verify(
+      *channel()->schema(), *channel()->schema()->root_table(),
+      static_cast<const uint8_t *>(message->context.data),
+      message->context.size))
+      << ": Corrupted flatbuffer on " << channel()->name()->c_str() << " "
+      << channel()->type()->c_str();
+
   next_queue_index_ = next_queue_index_.Increment();
 
   latest_message_ = message;