Add a new utility function to convert protozero to text proto format.

For now this has some limitations, but should be sufficient for our
needs. It is limited to TrackEvent fields and doesn't handle unknown
fields at all so the binary descriptor must be up to date.

Change-Id: Ifc6cd3fd587fae9556040f2d1baa5c976228c1f4

tools/gen_binary_descriptors

diff --git a/tools/gen_binary_descriptors b/tools/gen_binary_descriptors
index e980379..439d596 100755
--- a/tools/gen_binary_descriptors
+++ b/tools/gen_binary_descriptors
@@ -35,6 +35,8 @@
         'src/trace_processor/importers/proto/chrome_compositor_scheduler_state.descriptor.h',
     'src/protozero/test/example_proto/test_messages.proto':
         'src/protozero/test/example_proto/test_messages.descriptor.h',
+    'protos/perfetto/trace/track_event/track_event.proto':
+        'src/trace_processor/importers/proto/track_event.descriptor.h',
 }
 
 ROOT_DIR = os.path.dirname(os.path.dirname(os.path.realpath(__file__)))