Add protozero target for Chrome TrackEvent extensions

Bug: 171470675
Change-Id: I377272cc73f80a98efdeeed6d05c64bc23ea2630
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2489631Reviewed-by: Eric Seckler <eseckler@chromium.org>
Commit-Queue: Andrew Shulaev <ddrone@google.com>
Cr-Commit-Position: refs/heads/master@{#820171}

base/tracing/protos/BUILD.gn

@@ -2,6 +2,7 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import("//third_party/perfetto/gn/proto_library.gni")
 import("//third_party/protobuf/proto_library.gni")
 import("//tools/grit/grit_rule.gni")
 
@@ -15,6 +16,12 @@ proto_library("chrome_track_event") {
   generate_descriptor = "chrome_track_event.descriptor"
 }
 
+protozero_library("chrome_track_event_zero") {
+  perfetto_root_path = "//third_party/perfetto/"
+  sources = [ "chrome_track_event.proto" ]
+  import_dirs = [ "//third_party/perfetto/" ]
+}
+
 grit("chrome_track_event_resources") {
   source = "resources.grd"
   outputs = [