Add tracing support for mojo handle kinds

Support tracing of mojo handle and remote/receiver kinds. Thus provide
more precise debugging information for developers. Also avoid
generating fallback literals for base::trace_event::ValueToString.

Bug: 1103623
Change-Id: Ib01e79f7ae0aba64cabda3aea87cc1d1aed3b921
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2356005
Commit-Queue: Karel Král <karelkral@google.com>
Reviewed-by: Ken Rockot <rockot@google.com>
Reviewed-by: Alexander Timin <altimin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#798588}

mojo/public/tools/bindings/generators/cpp_tracing_support.py

@@ -362,6 +362,15 @@ def _WriteInputParamForTracingImpl(generator, kind, cpp_parameter_name,
     for line in _WrapIfNullable(loop_generator):
       yield line
     return
+  if (mojom.IsAnyHandleOrInterfaceKind(kind)
+      and not mojom.IsAssociatedInterfaceRequestKind(kind)):
+    yield output_context.AddSingleValue('Boolean',
+                                        cpp_parameter_name + '.is_valid()')
+    return
+  if mojom.IsAssociatedInterfaceRequestKind(kind):
+    yield output_context.AddSingleValue('Boolean',
+                                        cpp_parameter_name + '.is_pending()')
+    return
   yield output_context.AddSingleValue('String', _TraceEventToString())