TabManagerDelegate: Better prioritize ARC processes.

chrome/browser/chromeos/arc/arc_process.cc

 // Copyright 2016 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 "chrome/browser/chromeos/arc/arc_process.h"
 
+#include <utility>
+
 namespace arc {
 
 ArcProcess::ArcProcess(base::ProcessId nspid,
                        base::ProcessId pid,
                        const std::string& process_name,
-                       mojom::ProcessState process_state)
+                       mojom::ProcessState process_state,
+                       bool is_focused,
+                       int64_t last_activity_time)
     : nspid_(nspid),
       pid_(pid),
       process_name_(process_name),
-      process_state_(process_state) {}
+      process_state_(process_state),
+      is_focused_(is_focused),
+      last_activity_time_(last_activity_time) {}
 
 ArcProcess::~ArcProcess() = default;
 
+// Sort by (process_state, last_activity_time) pair.
+// Smaller process_state value means higher priority as defined in Android.
+// Larger last_activity_time means more recently used.
+bool ArcProcess::operator<(const ArcProcess& rhs) const {
+  return std::make_pair(process_state(), -last_activity_time()) <
+         std::make_pair(rhs.process_state(), -rhs.last_activity_time());
+}
+
 ArcProcess::ArcProcess(ArcProcess&& other) = default;
 ArcProcess& ArcProcess::operator=(ArcProcess&& other) = default;
 
 }  // namespace arc