[OBSOLETE] tracing v2: introduce TraceBufferWriter

components/tracing/BUILD.gn

Index: components/tracing/BUILD.gn
diff --git a/components/tracing/BUILD.gn b/components/tracing/BUILD.gn
index 1871b56cc1b42e19132f58d127de2eb0a94149af..52926f4df433c43b1fb82307a88f6dc19bdcb007 100644
--- a/components/tracing/BUILD.gn
+++ b/components/tracing/BUILD.gn
@@ -23,6 +23,8 @@ component("tracing") {
     "core/proto_zero_message_handle.h",
     "core/scattered_stream_writer.cc",
     "core/scattered_stream_writer.h",
+    "core/trace_buffer_writer.cc",
+    "core/trace_buffer_writer.h",
     "core/trace_ring_buffer.cc",
     "core/trace_ring_buffer.h",
     "tracing_export.h",
@@ -31,6 +33,7 @@ component("tracing") {
   defines = [ "TRACING_IMPLEMENTATION" ]
 
   deps = [
+    ":tracing_protos",
     "//base",
     "//ipc",
   ]
@@ -100,12 +103,14 @@ source_set("unit_tests") {
     "core/proto_utils_unittest.cc",
     "core/proto_zero_message_unittest.cc",
     "core/scattered_stream_writer_unittest.cc",
+    "core/trace_buffer_writer_unittest.cc",
     "core/trace_ring_buffer_unittest.cc",
     "test/fake_scattered_buffer.cc",
     "test/proto_zero_generation_unittest.cc",
   ]
 
   deps = [
+    ":golden_protos_for_tests",
     ":proto_zero_testing_messages",
     ":tracing",
     "//base/test:test_support",
@@ -119,3 +124,44 @@ source_set("unit_tests") {
     deps += [ ":startup_tracing" ]
   }
 }
+
+proto_library("golden_protos_for_tests") {
+  visibility = [ ":unit_tests" ]
+  proto_out_dir = "components/tracing/test/golden_protos"
+  sources = [
+    "proto/events_chunk.proto",
+  ]
+}
+
+proto_library("tracing_protos") {
+  visibility = [ "//components/tracing/*" ]
+
+  sources = [
+    "proto/event.proto",
+    "proto/event_args_for_testing.proto",
+    "proto/events_chunk.proto",
+  ]
+
+  generator_plugin_label = "tools/proto_zero_plugin:proto_zero_plugin"
+  generator_plugin_suffix = ".pbzero"
+  generate_cc = false
+  generate_python = false
+
+  # TODO(kraynov) Move away this complex path evaluation and dependency
+  # injection to proto_library.gni. All lines below should be removed.
+  # The problem is that root_out_dir and root_build_dir may differ in case of
+  # cross compilation. Also .exe will be appended on Windows.
+
+  plugin_host_label = generator_plugin_label + "($host_toolchain)"
+  generator_plugin =
+      rebase_path(get_label_info(plugin_host_label, "root_out_dir") + "/" +
+                      get_label_info(plugin_host_label, "name"),
+                  root_build_dir)
+  if (is_win) {
+    generator_plugin += ".exe"
+  }
+
+  deps = [
+    plugin_host_label,
+  ]
+}