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

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

Index: chrome/browser/chromeos/arc/process/arc_process.h
diff --git a/chrome/browser/chromeos/arc/process/arc_process.h b/chrome/browser/chromeos/arc/process/arc_process.h
index e2e6faf3b59cadd3fe1e62ce3a9caa0e10edc798..d728960ad721b07442e446b74fe49478dbd78a93 100644
--- a/chrome/browser/chromeos/arc/process/arc_process.h
+++ b/chrome/browser/chromeos/arc/process/arc_process.h
@@ -63,6 +63,9 @@ class ArcProcess {
   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);
 };