Enable tracing on Fuchsia (#3116)

content_handler/BUILD.gn

@@ -37,6 +37,7 @@ executable("content_handler") {
     "//flutter/sky/engine/platform",
     "//lib/ftl",
     "//lib/mtl",
+    "//lib/trace_event",
     "//lib/zip",
     "//mojo/public/cpp/application",
     "//mojo/public/cpp/bindings",

content_handler/main.cc

@@ -16,6 +16,7 @@
 #include "lib/ftl/tasks/task_runner.h"
 #include "lib/mtl/tasks/message_loop.h"
 #include "lib/mtl/threading/create_thread.h"
+#include "lib/trace_event/tracing_client.h"
 #include "mojo/public/cpp/application/application_impl_base.h"
 #include "mojo/public/cpp/application/connect.h"
 #include "mojo/public/cpp/application/run_application.h"
@@ -33,8 +34,10 @@ class App : public mojo::ApplicationImplBase {
  public:
   App() {}
   ~App() override {
-    if (initialized_)
+    if (initialized_) {
       StopThreads();
+      trace_event::DestroyTracer();
+    }
   }
 
   // Overridden from ApplicationDelegate:
@@ -42,6 +45,10 @@ class App : public mojo::ApplicationImplBase {
     FTL_DCHECK(!initialized_);
     initialized_ = true;
 
+    tracing::TraceProviderRegistryPtr registry;
+    ConnectToService(shell(), "mojo:tracing", GetProxy(&registry));
+    trace_event::InitializeTracer(std::move(registry));
+
     ftl::RefPtr<ftl::TaskRunner> gpu_task_runner;
     gpu_thread_ = mtl::CreateThread(&gpu_task_runner);
 

glue/BUILD.gn

@@ -29,6 +29,10 @@ source_set("glue") {
     deps += [
       "//lib/mtl",
     ]
+
+    public_deps = [
+      "//lib/trace_event",
+    ]
   } else {
     sources += [
       "drain_data_pipe_job_base.cc",

glue/trace_event.h

@@ -3,13 +3,7 @@
 // found in the LICENSE file.
 
 #if defined(__Fuchsia__)
-#define TRACE_EVENT0(a, b)
-#define TRACE_EVENT1(a, b, c, d)
-#define TRACE_EVENT2(a, b, c, d, e, f)
-#define TRACE_EVENT_ASYNC_BEGIN0(a, b, c)
-#define TRACE_EVENT_ASYNC_END0(a, b, c)
-#define TRACE_EVENT_ASYNC_BEGIN1(a, b, c, d, e)
-#define TRACE_EVENT_ASYNC_END1(a, b, c, d, e)
+#include "lib/trace_event/macros.h"
 #else
 #include "base/trace_event/trace_event.h"
 #endif  // defined(__Fuchsia__)