Re-land first pass BackgroundTracingManager.

content/public/browser/background_tracing_manager.h

+// 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.
+
+#ifndef CONTENT_PUBLIC_BROWSER_BACKGROUND_TRACING_MANAGER_H_
+#define CONTENT_PUBLIC_BROWSER_BACKGROUND_TRACING_MANAGER_H_
+
+#include "base/trace_event/trace_event_impl.h"
+#include "base/values.h"
+#include "content/common/content_export.h"
+
+namespace content {
+struct BackgroundTracingConfig;
+struct BackgroundTracingUploadConfig;
+
+// BackgroundTracingManager is used on the browser process to trigger the
+// collection of trace data and upload the results. Only the browser UI thread
+// is allowed to interact with the BackgroundTracingManager. All callbacks are
+// called on the UI thread.
+class BackgroundTracingManager {
+ public:
+  CONTENT_EXPORT static BackgroundTracingManager* GetInstance();
+
+  typedef base::Callback<void(base::RefCountedString*, base::Callback<void()>)>

[no sievers, 2015/05/20 19:22:39]

const base::RefCountedString*?

[no sievers, 2015/05/20 19:22:39]

nit: base::Callback<void()> -> base::Closure

[no sievers, 2015/05/20 19:22:40]

Can you document what the arguments are?
Esp. for the other callback it's unclear.

[shatch, 2015/05/20 19:53:55]

Done.

[shatch, 2015/05/20 19:53:55]

Done.

+      ReceiveCallback;
+
+  // Set the triggering rules for when to start recording.
+  //
+  // In preemptive mode, recording begins immediately and any calls to
+  // TriggerNamedEvent() will potentially trigger the trace to finalize and get
+  // uploaded to the specified upload_sink. Once the trace has been uploaded,
+  // tracing will be enabled again.
+  //
+  // In reactive mode, recording begins when TriggerNamedEvent() is called, and
+  // continues until either the next call to TriggerNamedEvent, or a timeout
+  // occurs. Tracing will not be re-enabled after the trace is finalized and
+  // uploaded to the upload_sink.
+  //
+  // Calls to SetActiveScenario() with a config will fail if tracing is
+  // currently on. Use WhenIdle to register a callback to get notified when
+  // the manager is idle and a config can be set again.
+  virtual bool SetActiveScenario(scoped_ptr<BackgroundTracingConfig> config,
+                                 const ReceiveCallback& receive_callback,
+                                 bool requires_anonymized_data) = 0;
+
+  // Notifies the caller when the manager is idle (not recording or uploading),
+  // so that a call to SetActiveScenario() is likely to succeed.
+  typedef base::Callback<void()> IdleCallback;
+  virtual void WhenIdle(IdleCallback idle_callback) = 0;
+
+  typedef base::Callback<void(bool)> StartedFinalizingCallback;
+  typedef int TriggerHandle;
+
+  // Notifies that a manual trigger event has occurred, and we may need to
+  // either begin recording or finalize the trace, depending on the config.
+  // If the trigger specified isn't active in the config, this will do nothing.
+  virtual void TriggerNamedEvent(
+      TriggerHandle,

[no sievers, 2015/05/20 19:22:39]

nit: 'TriggerHandle trigger_handle' for consistency

[shatch, 2015/05/20 19:53:55]

Done.

+      StartedFinalizingCallback started_callback) = 0;
+
+  // Registers a manual trigger handle, and returns a TriggerHandle which can
+  // be passed to DidTriggerHappen().
+  virtual TriggerHandle RegisterTriggerType(const char* trigger_name) = 0;
+
+  // Returns a list of all registered triggers.
+  virtual void GetTriggerNameList(std::vector<std::string>& trigger_names) = 0;

[no sievers, 2015/05/20 19:22:39]

nit: 'std::vector<std::string>*', by pointer when modified by callee per style
guide

[shatch, 2015/05/20 19:53:55]

Done.

+
+  virtual void InvalidateTriggerHandlesForTesting() = 0;
+
+ protected:
+  virtual ~BackgroundTracingManager() {}
+};
+
+}  // namespace content
+
+#endif  // CONTENT_PUBLIC_BROWSER_BACKGROUND_TRACING_MANAGER_H_