Refactor mojo parameter tracing code into a module

Refactor python code responsible for generating C++ function parameter
tracing of mojo methods into a standalone module.

Bug: 1103623
Change-Id: I39dff196c8227534a6141b0984559e2323ceaaec
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2346808
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@{#797586}

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

+# Copyright 2020 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+"""Implement the common methods used in mojom_cpp_generator.py and
+mojom_cpp_parameter_tracing.py in order to get rid of circular dependency."""
+
+import mojom.generate.module as mojom
+
+
+def IsNativeOnlyKind(kind):
+  return (mojom.IsStructKind(kind) or mojom.IsEnumKind(kind)) and \
+      kind.native_only

mojo/public/tools/bindings/mojom.gni

@@ -93,7 +93,9 @@ mojom_generator_root = "$_mojom_tools_root/bindings"
 mojom_generator_script = "$mojom_generator_root/mojom_bindings_generator.py"
 mojom_generator_sources =
     mojom_parser_sources + [
+      "$mojom_generator_root/generators/cpp_util.py",
       "$mojom_generator_root/generators/mojom_cpp_generator.py",
+      "$mojom_generator_root/generators/cpp_tracing_support.py",
       "$mojom_generator_root/generators/mojom_java_generator.py",
       "$mojom_generator_root/generators/mojom_mojolpm_generator.py",
       "$mojom_generator_root/generators/mojom_js_generator.py",