arc: enable Android tracing in verified-boot mode

content/browser/tracing/tracing_controller_impl.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 #include "content/browser/tracing/tracing_controller_impl.h"
 
 #include <algorithm>
 #include <memory>
 #include <utility>
 
 #include "base/bind.h"
@@ skipping 650 matching lines @@
 }
 
 void TracingControllerImpl::OnEndAgentTracingAcked(
     const std::string& agent_name,
     const std::string& events_label,
     const scoped_refptr<base::RefCountedString>& events_str_ptr) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 
   if (trace_data_sink_.get() && events_str_ptr &&
       !events_str_ptr->data().empty()) {
-    if (agent_name == kETWTracingAgentName) {
-      // The Windows kernel events are kept into a JSON format stored as string
-      // and must not be escaped.
-      trace_data_sink_->AddAgentTrace(events_label, events_str_ptr->data());
-    } else if (agent_name != kArcTracingAgentName) {
-      // ARC trace data is obtained via systrace. Ignore the empty data.
-      // Quote other trace data as JSON strings and merge them into
-      // |trace_data_sink_|.
-      trace_data_sink_->AddAgentTrace(
-          events_label, base::GetQuotedJSONString(events_str_ptr->data()));
+    std::string json_string;
+    if (agent_name == kETWTracingAgentName ||
+        agent_name == kArcTracingAgentName) {
+      // The Windows kernel events and ARC Android tracing event are kept
+      // into a JSON format stored as string and must not be escaped.
+      json_string = events_str_ptr->data();

[dcheng, 2017/04/06 06:14:14]

This copies the data string at least 2x now for Windows rather than just 1x.
Maybe just keep the original code, and add an additional else if branch for
ARC++.

[shunhsingou, 2017/04/06 08:42:28]

Done.

+    } else {
+      json_string = base::GetQuotedJSONString(events_str_ptr->data());
+    }
+
+    if (agent_name == kArcTracingAgentName) {
+      trace_data_sink_->AddTraceChunk(json_string);
+    } else {
+      trace_data_sink_->AddAgentTrace(events_label, json_string);
     }
   }
   std::vector<std::string> category_groups;
   OnStopTracingAcked(NULL, category_groups);
 }
 
 void TracingControllerImpl::OnTraceDataCollected(
     const scoped_refptr<base::RefCountedString>& events_str_ptr) {
   // OnTraceDataCollected may be called from any browser thread, either by the
   // local event trace system or from child processes via TraceMessageFilter.
@@ skipping 218 matching lines @@
 void TracingControllerImpl::RemoveTraceMessageFilterObserver(
     TraceMessageFilterObserver* observer) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   trace_message_filter_observers_.RemoveObserver(observer);
 
   for (auto& filter : trace_message_filters_)
     observer->OnTraceMessageFilterRemoved(filter.get());
 }
 
 }  // namespace content