Cleanup platform/BUILD.gn to mirror DEPS relationships.

Simplifies the BUILD.gn targets, to make dependency relationships very
clear.

Bug: openscreen:89
Change-Id: I8d0392ba04c3abe75464bfec3b789ce06fcb95d0
Reviewed-on: https://chromium-review.googlesource.com/c/openscreen/+/1952154
Reviewed-by: Jordan Bayles <jophba@chromium.org>
Reviewed-by: Yuri Wiitala <miu@chromium.org>
Reviewed-by: mark a. foltz <mfoltz@chromium.org>
Commit-Queue: Yuri Wiitala <miu@chromium.org>
diff --git a/platform/impl/task_runner.h b/platform/impl/task_runner.h
index bbdd1cc..b53bdc4 100644
--- a/platform/impl/task_runner.h
+++ b/platform/impl/task_runner.h
@@ -82,7 +82,7 @@
     // used. This simplifies switching between 'Task' and 'TaskWithMetadata'
     // based on the compilation flag.
     TaskWithMetadata(Task task)
-        : task_(std::move(task)), trace_ids_(TRACE_HIERARCHY){};
+        : task_(std::move(task)), trace_ids_(TRACE_HIERARCHY) {}
 
     void operator()() {
       TRACE_SET_HIERARCHY(trace_ids_);