Refactor CallStackProfile::Params into base/ for use over IPC.

base/metrics/call_stack_profile_params.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 BASE_METRICS_CALL_STACK_PROFILE_PARAMS_H_
+#define BASE_METRICS_CALL_STACK_PROFILE_PARAMS_H_
+
+#include "base/base_export.h"
+
+namespace base {
+
+// Stack profiling parameters for metrics collection.
+struct BASE_EXPORT CallStackProfileParams {

[Alexei Svitkine (slow), 2015/09/01 14:54:33]

Sorry, but to me this seems really out of place in base/, given that no code in
base/ is using it and that it's meaningless on its own.

You mention the motivation for this is to have non-browser processes send this
struct via IPC?

If it's just communication between non-browser process and browser process,
couldn't it live in chrome/common?

[sydli, 2015/09/01 16:39:42]

Some processes we'd like to profile (eg GPU) live in content. Would it be
reasonable to move this to content/common?

+  enum Trigger {
+    UNKNOWN,
+    PROCESS_STARTUP,
+    JANKY_TASK,
+    THREAD_HUNG,
+    TRIGGER_LAST = THREAD_HUNG
+  };
+
+  // If unspecified, sets |preserve_sample_ordering| to false.
+  explicit CallStackProfileParams(Trigger trigger);
+  CallStackProfileParams(Trigger trigger, bool preserve_sample_ordering);
+
+  // Default constructor exposed to satisfy IPC macros. Do not use explicitly.
+  CallStackProfileParams();
+
+  // The triggering event.
+  Trigger trigger;
+
+  // True if sample ordering is important and should be preserved when the
+  // associated profiles are compressed. This should only be set to true if
+  // the intended use of the requires that the sequence of call stacks within
+  // a particular profile be preserved. The default value of false provides
+  // better compression of the encoded profile and is sufficient for the
+  // typical use case of recording profiles for stack frequency analysis in
+  // aggregate.
+  bool preserve_sample_ordering;
+};
+
+}  // namespace base
+
+#endif  // BASE_METRICS_CALL_STACK_PROFILE_PARAMS_H_