Cleanup: Better constify some strings in chrome/browser/{chromeos,extensions}.

chrome/browser/extensions/activity_log/activity_log_policy.cc

Index: chrome/browser/extensions/activity_log/activity_log_policy.cc
diff --git a/chrome/browser/extensions/activity_log/activity_log_policy.cc b/chrome/browser/extensions/activity_log/activity_log_policy.cc
index 5b75bfd8604405e11b6a6ba04110b60ee1a35409..58c9f6b3e2960893b45a2c33a93b9609f1d465e6 100644
--- a/chrome/browser/extensions/activity_log/activity_log_policy.cc
+++ b/chrome/browser/extensions/activity_log/activity_log_policy.cc
@@ -25,8 +25,9 @@ namespace constants = activity_log_constants;
 namespace {
 // Obsolete database tables: these should be dropped from the database if
 // found.
-const char* kObsoleteTables[] = {"activitylog_apis", "activitylog_blocked",
-                                 "activitylog_urls"};
+const char* const kObsoleteTables[] = {"activitylog_apis",
+                                       "activitylog_blocked",
+                                       "activitylog_urls"};
 }  // namespace
 
 namespace extensions {