arc: enable Android tracing from chrome://tracing in dev mode

content/browser/tracing/tracing_controller_impl.cc

Index: content/browser/tracing/tracing_controller_impl.cc
diff --git a/content/browser/tracing/tracing_controller_impl.cc b/content/browser/tracing/tracing_controller_impl.cc
index 3686e85c0a765fe9eb7db5990b372d3f92ea1d5d..69ba16d7a1d6868892b7c725f929108bfc6078f4 100644
--- a/content/browser/tracing/tracing_controller_impl.cc
+++ b/content/browser/tracing/tracing_controller_impl.cc
@@ -3,6 +3,10 @@
 // found in the LICENSE file.
 #include "content/browser/tracing/tracing_controller_impl.h"
 
+#include <algorithm>
+#include <memory>
+#include <utility>
+
 #include "base/bind.h"
 #include "base/cpu.h"
 #include "base/files/file_util.h"
@@ -44,6 +48,7 @@
 #if defined(OS_CHROMEOS)
 #include "chromeos/dbus/dbus_thread_manager.h"
 #include "chromeos/dbus/debug_daemon_client.h"
+#include "chromeos/trace/arc_trace_agent.h"
 #endif
 
 #if defined(OS_WIN)
@@ -62,6 +67,7 @@ base::LazyInstance<TracingControllerImpl>::Leaky g_controller =
 
 const char kChromeTracingAgentName[] = "chrome";
 const char kETWTracingAgentName[] = "etw";
+const char kArcTracingAgentName[] = "arc";
 const char kChromeTraceLabel[] = "traceEvents";
 
 const int kStartTracingTimeoutSeconds = 30;
@@ -297,6 +303,17 @@ bool TracingControllerImpl::StartTracing(
 #endif
   }
 
+#if defined(OS_CHROMEOS)
+  auto* arc_trace_agent = chromeos::ArcTraceAgent::GetInstance();
+  if (arc_trace_agent) {

[Luis Héctor Chávez, 2017/02/16 16:45:11]

Why would |arc_trace_agent| be nullptr? Maybe you should follow the pattern that
the EtwTracingAgent uses. Same in L584.

[Earl Ou, 2017/02/17 02:12:59]

Done.

+    arc_trace_agent->StartAgentTracing(
+        trace_config,
+        base::Bind(&TracingControllerImpl::OnStartAgentTracingAcked,
+                   base::Unretained(this)));
+    ++pending_start_tracing_ack_count_;
+  }
+#endif
+
   // TraceLog may have been enabled in startup tracing before threads are ready.
   if (TraceLog::GetInstance()->IsEnabled())
     return true;
@@ -562,6 +579,12 @@ void TracingControllerImpl::AddTracingAgent(const std::string& agent_name) {
         BrowserThread::GetBlockingPool());
     return;
   }
+
+  auto* arc_trace_agent = chromeos::ArcTraceAgent::GetInstance();
+  if (arc_trace_agent && agent_name == arc_trace_agent->GetTracingAgentName()) {
+    additional_tracing_agents_.push_back(arc_trace_agent);
+    return;
+  }
 #elif defined(OS_WIN)
   auto* etw_agent = EtwTracingAgent::GetInstance();
   if (agent_name == etw_agent->GetTracingAgentName()) {
@@ -674,7 +697,11 @@ void TracingControllerImpl::OnEndAgentTracingAcked(
     } else {
       json_string = base::GetQuotedJSONString(events_str_ptr->data());
     }
-    trace_data_sink_->AddAgentTrace(events_label, json_string);
+
+    // ARC tracing data is obtained via systrace. Ignore the empty data here.
+    if (agent_name != kArcTracingAgentName) {
+      trace_data_sink_->AddAgentTrace(events_label, json_string);
+    }
   }
   std::vector<std::string> category_groups;
   OnStopTracingAcked(NULL, category_groups);
@@ -829,7 +856,7 @@ void TracingControllerImpl::RecordClockSyncMarker(
 
 void TracingControllerImpl::IssueClockSyncMarker() {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
-  DCHECK(pending_clock_sync_ack_count_ == 0);
+  DCHECK_EQ(0, pending_clock_sync_ack_count_);
 
   for (auto* it : additional_tracing_agents_) {
     if (it->SupportsExplicitClockSync()) {
@@ -869,7 +896,7 @@ void TracingControllerImpl::OnClockSyncMarkerRecordedByAgent(
     return;
 
   // Stop tracing only if all agents report back.
-  if(--pending_clock_sync_ack_count_ == 0) {
+  if (--pending_clock_sync_ack_count_ == 0) {
     clock_sync_timer_.Stop();
     StopTracingAfterClockSync();
   }