Allow backgrounding processes on Mac

base/process/process.h

 // Copyright 2011 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_PROCESS_PROCESS_H_
 #define BASE_PROCESS_PROCESS_H_
 
 #include "base/base_export.h"
 #include "base/macros.h"
 #include "base/process/process_handle.h"
 #include "base/time/time.h"
 #include "build/build_config.h"
 
 #if defined(OS_WIN)
 #include "base/win/scoped_handle.h"
 #endif
 
+#if defined(OS_MACOSX)
+#include "base/feature_list.h"
+#include "base/process/port_provider_mac.h"
+#endif
+
 namespace base {
 
+#if defined(OS_MACOSX)
+extern const Feature kMacAllowBackgroundingProcesses;
+#endif
+
 // Provides a move-only encapsulation of a process.
 //
 // This object is not tied to the lifetime of the underlying process: the
 // process may be killed and this object may still around, and it will still
 // claim to be valid. The actual behavior in that case is OS dependent like so:
 //
 // Windows: The underlying ProcessHandle will be valid after the process dies
 // and can be used to gather some information about that process, but most
 // methods will obviously fail.
 //
@@ skipping 69 matching lines @@
   // any process.
   // NOTE: |exit_code| is optional, nullptr can be passed if the exit code is
   // not required.
   bool WaitForExit(int* exit_code);
 
   // Same as WaitForExit() but only waits for up to |timeout|.
   // NOTE: |exit_code| is optional, nullptr can be passed if the exit code
   // is not required.
   bool WaitForExitWithTimeout(TimeDelta timeout, int* exit_code);
 
+#if defined(OS_MACOSX)
+  // The Mac needs a Mach port in order to manipulate a process's priority,
+  // and there's no good way to get that from base given the pid. These Mac
+  // variants of the IsProcessBackgrounded and SetProcessBackgrounded API take
+  // a port provider for this reason. See crbug.com/460102
+  //
+  // A process is backgrounded when its task priority is
+  // |TASK_BACKGROUND_APPLICATION|.
+  //
+  // Returns true if the port_provider can locate a task port for the process
+  // and it is backgrounded. If port_provider is null, returns false.
+  bool IsProcessBackgrounded(PortProvider* port_provider) const;
+
+  // Set the process as backgrounded. If value is
+  // true, the priority of the associated task will be set to
+  // TASK_BACKGROUND_APPLICATION. If value is false, the
+  // priority of the process will be set to TASK_FOREGROUND_APPLICATION.
+  //
+  // Returns true if the priority was changed, false otherwise. If
+  // |port_provider| is null, this is a no-op and it returns false.
+  bool SetProcessBackgrounded(PortProvider* port_provider, bool value);
+#else
   // A process is backgrounded when it's priority is lower than normal.
   // Return true if this process is backgrounded, false otherwise.
   bool IsProcessBackgrounded() const;
 
   // Set a process as backgrounded. If value is true, the priority of the
   // process will be lowered. If value is false, the priority of the process
   // will be made "normal" - equivalent to default process priority.
   // Returns true if the priority was changed, false otherwise.
   bool SetProcessBackgrounded(bool value);
-
+#endif  // defined(OS_MACOSX)
   // Returns an integer representing the priority of a process. The meaning
   // of this value is OS dependent.
   int GetPriority() const;
 
 #if defined(OS_CHROMEOS)
   // Get the PID in its PID namespace.
   // If the process is not in a PID namespace or /proc/<pid>/status does not
   // report NSpid, kNullProcessId is returned.
   ProcessId GetPidInNamespace() const;
 #endif
@@ skipping 13 matching lines @@
 // Exposed for testing.
 // Given the contents of the /proc/<pid>/cgroup file, determine whether the
 // process is backgrounded or not.
 BASE_EXPORT bool IsProcessBackgroundedCGroup(
     const StringPiece& cgroup_contents);
 #endif  // defined(OS_CHROMEOS)
 
 }  // namespace base
 
 #endif  // BASE_PROCESS_PROCESS_H_