Profiling process topology

chrome/browser/profiling_host/profiling_process_host.h

+// Copyright 2017 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 CHROME_BROWSER_PROFILING_HOST_PROFILING_PROCESS_HOST_H_
+#define CHROME_BROWSER_PROFILING_HOST_PROFILING_PROCESS_HOST_H_
+
+#include "base/macros.h"
+#include "base/process/process.h"
+
+namespace base {
+class CommandLine;
+}
+
+namespace profiling {
+
+// Represents the browser side of the profiling process (//chrome/profiling).
+//
+// The profiling process is a singleton. The profiling process infrastructure
+// is implemented in the Chrome layer so doesn't depend on the content
+// infrastructure for managing child processes.
+//
+// Not thread safe. Should be used on the browser UI thread only.
+//
+// The profing process host can be started normally while Chrome is running,
+// but can also start in a partial mode where the memory logging connections
+// are active but the Mojo control channel has not yet been connected. This is
+// to support starting the profiling process very early in the startup
+// process (to get most memory events) before other infrastructure like the
+// I/O thread has been started.
+class ProfilingProcessHost {
+ public:
+  // Launches the profiling process if necessary and returns a pointer to it.
+  static ProfilingProcessHost* EnsureStarted();
+
+  // Returns a pointer to the current global profiling process host or, if
+  // no profiling process is launched, null.

[awong, 2017/06/29 18:39:32]

null -> nullptr

+  static ProfilingProcessHost* Get();
+
+  // Appends necessary switches to a command line for a child process. These
+  // switches will causse the child process to start in the profiling mode
+  // currently active.

[awong, 2017/06/29 18:39:32]

"Appends necessary switches to a command line for a child process" -> "Appends
necessary switches to a command line for a child process so it can be profiled"

"causse" -> "cause"

"start in the profiling mode currently active" <-- that doesn't parse... can you
reword?

+  static void AddSwitchesToChildCmdLine(base::CommandLine* child_cmd_line);
+
+ private:
+  ProfilingProcessHost();
+  ~ProfilingProcessHost();
+
+  void Launch();
+
+  // Use process_.IsValid() to determine if the child process has been launched.
+  base::Process process_;
+  std::string pipe_id_;
+
+  DISALLOW_COPY_AND_ASSIGN(ProfilingProcessHost);
+};
+
+}  // namespace profiling
+
+#endif  // CHROME_BROWSER_PROFILING_HOST_PROFILING_PROCESS_HOST_H_