TabManager: Add more logs to understand how it works when memory is low.

chrome/browser/chromeos/arc/process/arc_process.h

 // 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.
 
 #ifndef CHROME_BROWSER_CHROMEOS_ARC_PROCESS_ARC_PROCESS_H_
 #define CHROME_BROWSER_CHROMEOS_ARC_PROCESS_ARC_PROCESS_H_
 
 #include <stdint.h>
 #include <string>
 #include <vector>
@@ skipping 34 matching lines @@
   std::string process_name_;
   mojom::ProcessState process_state_;
   // If the Android app is the focused window.
   bool is_focused_;
   // A monotonic timer recording the last time this process was active.
   // Milliseconds since Android boot. This info is passed from Android
   // ActivityManagerService via IPC.
   int64_t last_activity_time_;
   std::vector<std::string> packages_;
 
+  friend std::ostream& operator<<(std::ostream& out,
+                                  const ArcProcess& arc_process);
+
   DISALLOW_COPY_AND_ASSIGN(ArcProcess);
 };
 
 }  // namespace arc
 
 #endif  // CHROME_BROWSER_CHROMEOS_ARC_PROCESS_ARC_PROCESS_H_