Adds a callback to TracingAgent::StartAgentTracing()

chromeos/dbus/debug_daemon_client.cc

Index: chromeos/dbus/debug_daemon_client.cc
diff --git a/chromeos/dbus/debug_daemon_client.cc b/chromeos/dbus/debug_daemon_client.cc
index 5358c9419e3002796764837db46616d97212b2a6..a5019a1571c2c7df1da29054ed075a1c15e326ff 100644
--- a/chromeos/dbus/debug_daemon_client.cc
+++ b/chromeos/dbus/debug_daemon_client.cc
@@ -20,6 +20,7 @@
 #include "base/posix/eintr_wrapper.h"
 #include "base/strings/string_util.h"
 #include "base/task_runner_util.h"
+#include "base/thread_task_runner_handle.h"
 #include "chromeos/dbus/pipe_reader.h"
 #include "dbus/bus.h"
 #include "dbus/message.h"
@@ -206,8 +207,8 @@ class DebugDaemonClientImpl : public DebugDaemonClient {
 
   std::string GetTraceEventLabel() override { return kCrOSTraceLabel; }
 
-  bool StartAgentTracing(
-      const base::trace_event::TraceConfig& trace_config) override {
+  void StartAgentTracing(const base::trace_event::TraceConfig& trace_config,
+                         const StartAgentTracingCallback& callback) override {
     dbus::MethodCall method_call(
         debugd::kDebugdInterface,
         debugd::kSystraceStart);
@@ -220,7 +221,9 @@ class DebugDaemonClientImpl : public DebugDaemonClient {
         dbus::ObjectProxy::TIMEOUT_USE_DEFAULT,
         base::Bind(&DebugDaemonClientImpl::OnStartMethod,
                    weak_ptr_factory_.GetWeakPtr()));
-    return true;
+
+    base::ThreadTaskRunnerHandle::Get()->PostTask(
+        FROM_HERE, base::Bind(callback, GetTracingAgentName(), true));

[stevenjb, 2016/01/26 20:11:19]

Document |success|, i.e: true /* success */

[charliea (OOO until 10-5), 2016/01/26 20:29:56]

Ah, didn't know that you were supposed to do this. Done.

   }
 
   void StopAgentTracing(const StopAgentTracingCallback& callback) override {