Wire up mojo tracing (#3047)

* Wire up to mojo::tracing::* infrastructure.

* Initialize tracing as early as possible.

* Make dependency specific to fuchsia.

content_handler/BUILD.gn

@@ -36,6 +36,7 @@ executable("content_handler") {
     "//lib/ftl",
     "//lib/mtl",
     "//lib/zip",
+    "//mojo/public/c",
     "//mojo/public/cpp/application",
     "//mojo/public/cpp/bindings",
     "//mojo/public/cpp/system",
@@ -43,6 +44,7 @@ executable("content_handler") {
     "//mojo/services/asset_bundle/interfaces",
     "//mojo/services/content_handler/interfaces",
     "//mojo/services/framebuffer/interfaces",
+    "//mojo/services/tracing/cpp",
     "//mojo/system",
     "//third_party/skia",
 

content_handler/main.cc

@@ -21,6 +21,7 @@
 #include "mojo/public/cpp/application/run_application.h"
 #include "mojo/public/cpp/application/service_provider_impl.h"
 #include "mojo/services/content_handler/interfaces/content_handler.mojom.h"
+#include "mojo/services/tracing/cpp/tracing_client.h"
 
 namespace flutter_content_handler {
 namespace {
@@ -33,8 +34,10 @@ class App : public mojo::ApplicationImplBase {
  public:
   App() {}
   ~App() override {
-    if (initialized_)
+    if (initialized_) {
       StopThreads();
+      mojo::tracing::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));
+    mojo::tracing::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 = [
+      "//mojo/services/tracing/cpp",
+    ]
   } 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 "mojo/services/tracing/cpp/macros.h"
 #else
 #include "base/trace_event/trace_event.h"
 #endif  // defined(__Fuchsia__)