Make tracing work on Android

sky/tools/debugger/prompt/trace_collector.h

Index: sky/tools/debugger/prompt/trace_collector.h
diff --git a/sky/tools/debugger/prompt/trace_collector.h b/sky/tools/debugger/prompt/trace_collector.h
new file mode 100644
index 0000000000000000000000000000000000000000..773a4021442c665fcc8b266be9c7946d03cb0a17
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+++ b/sky/tools/debugger/prompt/trace_collector.h
@@ -0,0 +1,40 @@
+// Copyright 2014 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.
+
+#ifndef SKY_TOOLS_DEBUGGER_PROMPT_TRACE_COLLECTOR_H_
+#define SKY_TOOLS_DEBUGGER_PROMPT_TRACE_COLLECTOR_H_
+
+#include <vector>
+
+#include "base/callback.h"
+#include "mojo/common/data_pipe_drainer.h"
+
+namespace sky {
+namespace debugger {
+
+class TraceCollector : public mojo::common::DataPipeDrainer::Client {
+ public:
+  typedef base::Callback<void(std::string)> TraceCallback;
+
+  explicit TraceCollector(mojo::ScopedDataPipeConsumerHandle source);
+  ~TraceCollector();
+
+  void GetTrace(TraceCallback callback);
+
+ private:
+  void OnDataAvailable(const void* data, size_t num_bytes) override;
+  void OnDataComplete() override;
+
+  std::string GetTraceAsString();
+
+  mojo::common::DataPipeDrainer drainer_;
+  std::vector<char> trace_;
+  bool is_complete_;
+  TraceCallback callback_;
+};
+
+}  // namespace debugger
+}  // namespace sky
+
+#endif  // SKY_TOOLS_DEBUGGER_PROMPT_TRACE_COLLECTOR_H_