[Fuchsia] Switch to cwriter tracing API.

runtime/vm/timeline.h

Index: runtime/vm/timeline.h
diff --git a/runtime/vm/timeline.h b/runtime/vm/timeline.h
index d1954510deee658ae30eec8e3b5779fa283bfc9f..2d9a871cf1ebb0bf73488831c46b6f3ed8c37253 100644
--- a/runtime/vm/timeline.h
+++ b/runtime/vm/timeline.h
@@ -753,7 +753,7 @@ class TimelineEventSystraceRecorder : public TimelineEventFixedBufferRecorder {
 class TimelineEventFuchsiaRecorder : public TimelineEventFixedBufferRecorder {
  public:
   explicit TimelineEventFuchsiaRecorder(intptr_t capacity = kDefaultCapacity);
-  virtual ~TimelineEventFuchsiaRecorder() {}
+  virtual ~TimelineEventFuchsiaRecorder();
 
   const char* name() const { return "Fuchsia"; }