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 f4ee65c687186e771038bd9f6f2b6f1c135e9a0d..e823411a4cdcde4b6aeb6b507ee7e4bfe69c6ac2 100644
--- a/chrome/browser/chromeos/arc/process/arc_process.h
+++ b/chrome/browser/chromeos/arc/process/arc_process.h
@@ -52,6 +52,9 @@ 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);
 };