Make tracing work on Android

sky/tools/debugger/prompt/trace_collector.cc

Index: sky/tools/debugger/prompt/trace_collector.cc
diff --git a/sky/tools/debugger/prompt/trace_collector.cc b/sky/tools/debugger/prompt/trace_collector.cc
new file mode 100644
index 0000000000000000000000000000000000000000..9ce379b3669650386ad4f1f997eb71bcbdbbee25
--- /dev/null
+++ b/sky/tools/debugger/prompt/trace_collector.cc
@@ -0,0 +1,47 @@
+// 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.
+
+#include "sky/tools/debugger/prompt/trace_collector.h"
+
+namespace sky {
+namespace debugger {
+
+TraceCollector::TraceCollector(mojo::ScopedDataPipeConsumerHandle source)
+    : drainer_(this, source.Pass()),
+      is_complete_(false),
+      callback_requested_(false) {
+}
+
+TraceCollector::~TraceCollector() {
+}
+
+void TraceCollector::GetTrace(TraceCallback callback) {
+  DCHECK(!callback_requested_);
+  if (is_complete_) {
+    callback.Run(GetTraceAsString());
+    return;
+  }
+  callback_requested_ = true;
+  callback_ = callback;
+}
+
+void TraceCollector::OnDataAvailable(const void* data, size_t num_bytes) {
+  DCHECK(!is_complete_);
+  const char* chars = static_cast<const char*>(data);
+  trace_.insert(trace_.end(), chars, chars + num_bytes);
+}
+
+void TraceCollector::OnDataComplete() {
+  DCHECK(!is_complete_);
+  is_complete_ = true;
+  if (callback_requested_)

[jamesr, 2015/01/15 23:56:58]

can't you just check if callback_ is null and clear it when you run it?

[abarth-chromium, 2015/01/16 00:31:53]

Done.

+    callback_.Run(GetTraceAsString());
+}
+
+std::string TraceCollector::GetTraceAsString() {
+  return std::string(&trace_.front(), trace_.size());
+}
+
+}  // namespace debugger
+}  // namespace sky