Support for tracing app initialization.

shell/tracer.cc

Index: shell/tracer.cc
diff --git a/shell/tracer.cc b/shell/tracer.cc
index ff0400d9f799cc087d612fe037c1c3df7b3613a3..62925f2ae26a31624fe6fb4a57e9adff1f3d35cf 100644
--- a/shell/tracer.cc
+++ b/shell/tracer.cc
@@ -17,11 +17,12 @@
 namespace shell {
 
 Tracer::Tracer()
-    : tracing_(false), first_chunk_written_(false), trace_file_(nullptr) {
-}
+    : trace_provider_binding_(&trace_provider_impl_),
+      tracing_(false),
+      first_chunk_written_(false),
+      trace_file_(nullptr) {}
 
-Tracer::~Tracer() {
-}
+Tracer::~Tracer() {}
 
 void Tracer::Start(const std::string& categories,
                    const std::string& duration_seconds_str,
@@ -67,8 +68,11 @@ void Tracer::StopAndFlushToFile() {
 
 void Tracer::ConnectToProvider(
     mojo::InterfaceRequest<tracing::TraceProvider> request) {
-  auto impl = new mojo::TraceProviderImpl(request.Pass());
-  impl->set_tracing_already_started(tracing_);
+  if (!trace_provider_binding_.is_bound()) {
+    trace_provider_binding_.Bind(request.Pass());
+  } else {
+    LOG(ERROR) << "Cannot accept two connections to TraceProvider.";
+  }
 }
 
 void Tracer::StopTracingAndFlushToDisk() {