Trace-based benchmarking via a mojo app.

apps/benchmark/trace_collector_client.cc

Index: apps/benchmark/trace_collector_client.cc
diff --git a/apps/benchmark/trace_collector_client.cc b/apps/benchmark/trace_collector_client.cc
new file mode 100644
index 0000000000000000000000000000000000000000..1d1483db2887f4832302331845fd5824691d74f3
--- /dev/null
+++ b/apps/benchmark/trace_collector_client.cc
@@ -0,0 +1,42 @@
+// Copyright 2015 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 "apps/benchmark/trace_collector_client.h"
+
+TraceCollectorClient::TraceCollectorClient(Receiver* receiver,
+                                           tracing::TraceCollectorPtr collector)
+    : receiver_(receiver),
+      collector_(collector.Pass()),
+      currently_tracing_(false) {}
+
+TraceCollectorClient::~TraceCollectorClient() {}
+
+void TraceCollectorClient::Start(const std::string& categories) {
+  DCHECK(!currently_tracing_);
+  currently_tracing_ = true;
+  mojo::DataPipe data_pipe;
+  collector_->Start(data_pipe.producer_handle.Pass(), categories);
+  drainer_.reset(new mojo::common::DataPipeDrainer(
+      this, data_pipe.consumer_handle.Pass()));
+  trace_data_.clear();
+  trace_data_ += "[";
+}
+
+void TraceCollectorClient::Stop() {
+  DCHECK(currently_tracing_);
+  currently_tracing_ = false;
+  collector_->StopAndFlush();
+}
+
+void TraceCollectorClient::OnDataAvailable(const void* data, size_t num_bytes) {
+  const char* chars = static_cast<const char*>(data);
+  trace_data_.append(chars, num_bytes);
+}
+
+void TraceCollectorClient::OnDataComplete() {
+  drainer_.reset();
+  collector_.reset();
+  trace_data_ += "]";
+  receiver_->OnTraceCollected(trace_data_);
+}