Add support for backgrounding processes on the Mac

Added process_mac.cc with implementations of IsProcessBackgrounded() and
SetProcessBackgrounded().

BUG=460102

Originally Committed: https://crrev.com/e3bb10f7860a1d553c85293bd7d7615c0e7f0fd9
Reverted: https://crrev.com/ce6226a7ffe2c1cb7ac5f6cf34b56b8d217686b9

Review URL: https://codereview.chromium.org/989703002

Cr-Commit-Position: refs/heads/master@{#330464}

base/base.gypi

@@ -485,6 +485,7 @@
           'process/process_iterator_openbsd.cc',
           'process/process_iterator_win.cc',
           'process/process_linux.cc',
+          'process/process_mac.cc',
           'process/process_metrics.cc',
           'process/process_metrics.h',
           'process/process_metrics_freebsd.cc',

base/process/BUILD.gn

@@ -41,6 +41,7 @@ source_set("process") {
     "process_iterator_openbsd.cc",
     "process_iterator_win.cc",
     "process_linux.cc",
+    "process_mac.cc",
     "process_metrics.cc",
     "process_metrics.h",
     "process_metrics_freebsd.cc",

base/process/process.h

-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// 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.
 
@@ -107,6 +107,24 @@ class BASE_EXPORT Process {
   // Same as WaitForExit() but only waits for up to |timeout|.
   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
+  // the Mach port for this reason. See crbug.com/460102
+  //
+  // A process is backgrounded when its priority is lower than normal.
+  // Return true if the process with mach port |task_port| is backgrounded,
+  // false otherwise.
+  bool IsProcessBackgrounded(mach_port_t task_port) const;
+
+  // Set the process with the specified mach port 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(mach_port_t task_port, 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;
@@ -116,7 +134,7 @@ class BASE_EXPORT 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;

base/process/process_mac.cc

+// 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.
+
+#include "base/process/process.h"
+
+#include "base/mac/mac_util.h"
+#include "base/mac/mach_logging.h"
+
+#include <mach/mach.h>
+
+// The following was added to <mach/task_policy.h> after 10.8.
+// TODO(shrike): Remove the TASK_OVERRIDE_QOS_POLICY ifndef once builders
+// reach 10.9 or higher.
+#ifndef TASK_OVERRIDE_QOS_POLICY
+
+#define TASK_OVERRIDE_QOS_POLICY 9
+
+typedef struct task_category_policy task_category_policy_data_t;
+typedef struct task_category_policy* task_category_policy_t;
+
+enum task_latency_qos {
+  LATENCY_QOS_TIER_UNSPECIFIED = 0x0,
+  LATENCY_QOS_TIER_0 = ((0xFF << 16) | 1),
+  LATENCY_QOS_TIER_1 = ((0xFF << 16) | 2),
+  LATENCY_QOS_TIER_2 = ((0xFF << 16) | 3),
+  LATENCY_QOS_TIER_3 = ((0xFF << 16) | 4),
+  LATENCY_QOS_TIER_4 = ((0xFF << 16) | 5),
+  LATENCY_QOS_TIER_5 = ((0xFF << 16) | 6)
+};
+typedef integer_t task_latency_qos_t;
+enum task_throughput_qos {
+  THROUGHPUT_QOS_TIER_UNSPECIFIED = 0x0,
+  THROUGHPUT_QOS_TIER_0 = ((0xFE << 16) | 1),
+  THROUGHPUT_QOS_TIER_1 = ((0xFE << 16) | 2),
+  THROUGHPUT_QOS_TIER_2 = ((0xFE << 16) | 3),
+  THROUGHPUT_QOS_TIER_3 = ((0xFE << 16) | 4),
+  THROUGHPUT_QOS_TIER_4 = ((0xFE << 16) | 5),
+  THROUGHPUT_QOS_TIER_5 = ((0xFE << 16) | 6),
+};
+
+#define LATENCY_QOS_LAUNCH_DEFAULT_TIER LATENCY_QOS_TIER_3
+#define THROUGHPUT_QOS_LAUNCH_DEFAULT_TIER THROUGHPUT_QOS_TIER_3
+
+typedef integer_t task_throughput_qos_t;
+
+struct task_qos_policy {
+  task_latency_qos_t task_latency_qos_tier;
+  task_throughput_qos_t task_throughput_qos_tier;
+};
+
+typedef struct task_qos_policy* task_qos_policy_t;
+#define TASK_QOS_POLICY_COUNT \
+  ((mach_msg_type_number_t)(sizeof(struct task_qos_policy) / sizeof(integer_t)))
+
+#endif  // TASK_OVERRIDE_QOS_POLICY
+
+namespace base {
+
+bool Process::CanBackgroundProcesses() {
+  return true;
+}
+
+bool Process::IsProcessBackgrounded(mach_port_t task_port) const {
+  // See SetProcessBackgrounded().
+  DCHECK(IsValid());
+  DCHECK_NE(task_port, TASK_NULL);
+
+  task_category_policy_data_t category_policy;
+  mach_msg_type_number_t task_info_count = TASK_CATEGORY_POLICY_COUNT;
+  boolean_t get_default = FALSE;
+
+  kern_return_t result =
+      task_policy_get(task_port, TASK_CATEGORY_POLICY,
+                      reinterpret_cast<task_policy_t>(&category_policy),
+                      &task_info_count, &get_default);
+  MACH_LOG_IF(ERROR, result != KERN_SUCCESS, result) <<
+      "task_policy_get TASK_CATEGORY_POLICY";
+
+  if (result == KERN_SUCCESS && get_default == FALSE) {
+    return category_policy.role == TASK_BACKGROUND_APPLICATION;
+  }
+  return false;
+}
+
+bool Process::SetProcessBackgrounded(mach_port_t task_port, bool background) {
+  DCHECK(IsValid());
+  DCHECK_NE(task_port, TASK_NULL);
+
+  if (!CanBackgroundProcesses()) {
+    return false;
+  }
+
+  task_category_policy category_policy;
+  category_policy.role =
+      background ? TASK_BACKGROUND_APPLICATION : TASK_FOREGROUND_APPLICATION;
+  kern_return_t result =
+      task_policy_set(task_port, TASK_CATEGORY_POLICY,
+                      reinterpret_cast<task_policy_t>(&category_policy),
+                      TASK_CATEGORY_POLICY_COUNT);
+
+  if (result != KERN_SUCCESS) {
+    MACH_LOG(ERROR, result) << "task_policy_set TASK_CATEGORY_POLICY";
+    return false;
+  } else if (!mac::IsOSMavericksOrLater()) {
+    return true;
+  }
+
+  // Latency QoS regulates timer throttling/accuracy. Select default tier
+  // on foreground because precise timer firing isn't needed.
+  struct task_qos_policy qos_policy = {
+      background ? LATENCY_QOS_TIER_5 : LATENCY_QOS_TIER_UNSPECIFIED,
+      background ? THROUGHPUT_QOS_TIER_5 : THROUGHPUT_QOS_TIER_UNSPECIFIED
+  };
+  result = task_policy_set(task_port, TASK_OVERRIDE_QOS_POLICY,
+                           reinterpret_cast<task_policy_t>(&qos_policy),
+                           TASK_QOS_POLICY_COUNT);
+  if (result != KERN_SUCCESS) {
+    MACH_LOG(ERROR, result) << "task_policy_set TASK_OVERRIDE_QOS_POLICY";
+    return false;
+  }
+
+  return true;
+}
+
+}  // namespace base

base/process/process_posix.cc

-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// 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.
 
@@ -253,12 +253,12 @@ Process Process::DeprecatedGetProcessFromHandle(ProcessHandle handle) {
   return Process(handle);
 }
 
-#if !defined(OS_LINUX)
+#if !defined(OS_LINUX) && !defined(OS_MACOSX)
 // static
 bool Process::CanBackgroundProcesses() {
   return false;
 }
-#endif  // !defined(OS_LINUX)
+#endif  // !defined(OS_LINUX) && !defined(OS_MACOSX)
 
 bool Process::IsValid() const {
   return process_ != kNullProcessHandle;
@@ -353,7 +353,7 @@ bool Process::WaitForExitWithTimeout(TimeDelta timeout, int* exit_code) {
   return WaitForExitWithTimeoutImpl(Handle(), exit_code, timeout);
 }
 
-#if !defined(OS_LINUX)
+#if !defined(OS_LINUX) && !defined(OS_MACOSX)
 bool Process::IsProcessBackgrounded() const {
   // See SetProcessBackgrounded().
   DCHECK(IsValid());
@@ -361,13 +361,13 @@ bool Process::IsProcessBackgrounded() const {
 }
 
 bool Process::SetProcessBackgrounded(bool value) {
-  // POSIX only allows lowering the priority of a process, so if we
-  // were to lower it we wouldn't be able to raise it back to its initial
-  // priority.
-  DCHECK(IsValid());
+  // Not implemented for POSIX systems other than Mac and Linux. With POSIX, if
+  // we were to lower the process priority we wouldn't be able to raise it back
+  // to its initial priority.
+  NOTIMPLEMENTED();
   return false;
 }
-#endif  // !defined(OS_LINUX)
+#endif  // !defined(OS_LINUX) && !defined(OS_MACOSX)
 
 int Process::GetPriority() const {
   DCHECK(IsValid());

base/process/process_unittest.cc

@@ -11,6 +11,10 @@
 #include "testing/gtest/include/gtest/gtest.h"
 #include "testing/multiprocess_func_list.h"
 
+#if defined(OS_MACOSX)
+#include <mach/mach.h>
+#endif  // OS_MACOSX
+
 namespace {
 
 #if defined(OS_WIN)
@@ -170,7 +174,19 @@ TEST_F(ProcessTest, WaitForExitWithTimeout) {
 TEST_F(ProcessTest, SetProcessBackgrounded) {
   Process process(SpawnChild("SimpleChildProcess"));
   int old_priority = process.GetPriority();
-#if defined(OS_WIN)
+#if defined(OS_MACOSX)
+  // On the Mac, backgrounding a process requires a port to that process.
+  // In the browser it's available through the MachBroker class, which is not
+  // part of base. Additionally, there is an indefinite amount of time between
+  // spawning a process and receiving its port. Because this test just checks
+  // the ability to background/foreground a process, we can use the current
+  // process's port instead.
+  mach_port_t process_port = mach_task_self();
+  EXPECT_TRUE(process.SetProcessBackgrounded(process_port, true));
+  EXPECT_TRUE(process.IsProcessBackgrounded(process_port));
+  EXPECT_TRUE(process.SetProcessBackgrounded(process_port, false));
+  EXPECT_FALSE(process.IsProcessBackgrounded(process_port));
+#elif defined(OS_WIN)
   EXPECT_TRUE(process.SetProcessBackgrounded(true));
   EXPECT_TRUE(process.IsProcessBackgrounded());
   EXPECT_TRUE(process.SetProcessBackgrounded(false));
@@ -188,7 +204,13 @@ TEST_F(ProcessTest, SetProcessBackgrounded) {
 TEST_F(ProcessTest, SetProcessBackgroundedSelf) {
   Process process = Process::Current();
   int old_priority = process.GetPriority();
-#if defined(OS_WIN)
+#if defined(OS_MACOSX)
+  mach_port_t process_port = mach_task_self();
+  EXPECT_TRUE(process.SetProcessBackgrounded(process_port, true));
+  EXPECT_TRUE(process.IsProcessBackgrounded(process_port));
+  EXPECT_TRUE(process.SetProcessBackgrounded(process_port, false));
+  EXPECT_FALSE(process.IsProcessBackgrounded(process_port));
+#elif defined(OS_WIN)
   EXPECT_TRUE(process.SetProcessBackgrounded(true));
   EXPECT_TRUE(process.IsProcessBackgrounded());
   EXPECT_TRUE(process.SetProcessBackgrounded(false));

content/browser/child_process_launcher.cc

-// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Copyright 2012 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.
 
@@ -269,7 +269,15 @@ void TerminateOnLauncherThread(bool zygote, base::Process process) {
 void SetProcessBackgroundedOnLauncherThread(base::Process process,
                                             bool background) {
   DCHECK_CURRENTLY_ON(BrowserThread::PROCESS_LAUNCHER);
+#if defined(OS_MACOSX)
+  MachBroker* broker = MachBroker::GetInstance();
+  mach_port_t task_port = broker->TaskForPid(process.Pid());
+  if (task_port != TASK_NULL) {
+    process.SetProcessBackgrounded(task_port, background);
+  }
+#else
   process.SetProcessBackgrounded(background);
+#endif  // defined(OS_MACOSX)
 #if defined(OS_ANDROID)
   SetChildProcessInForeground(process.Handle(), !background);
 #endif

content/browser/renderer_host/render_process_host_impl.cc

-// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Copyright 2012 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.
 
@@ -2211,14 +2211,15 @@ void RenderProcessHostImpl::SetBackgrounded(bool backgrounded) {
     return;
 #endif  // OS_WIN
 
-#if defined(OS_WIN)
-  // Same as below, but bound to an experiment (http://crbug.com/458594)
-  // initially on Windows. Enabled by default in the asbence of field trials to
-  // get coverage on the perf waterfall.
+#if defined(OS_WIN) || defined(OS_MACOSX)
+  // Same as below, but bound to an experiment (http://crbug.com/458594 on
+  // Windows, http://crbug.com/398103 on the Mac). Enabled by default in the
+  // absence of field trials to get coverage on the perf waterfall.
   base::FieldTrial* trial =
       base::FieldTrialList::Find("BackgroundRendererProcesses");
-  if (!trial || trial->group_name() != "Disallow")
+  if (!trial || !StartsWithASCII(trial->group_name(), "Disallow", true)) {
     child_process_launcher_->SetProcessBackgrounded(backgrounded);
+  }
 #else
   // Control the background state from the browser process, otherwise the task
   // telling the renderer to "unbackground" itself may be preempted by other