Cleanup: Better constify some strings in base.

Fix some lint errors along the way.

Review URL: https://codereview.chromium.org/632103004

Cr-Commit-Position: refs/heads/master@{#300407}


CrOS-Libchrome-Original-Commit: 073d514d518521a5c409d5037b45e0a46602c997
diff --git a/base/files/file_path.cc b/base/files/file_path.cc
index 11bf69d..bf37be6 100644
--- a/base/files/file_path.cc
+++ b/base/files/file_path.cc
@@ -35,8 +35,8 @@
 
 namespace {
 
-const char* kCommonDoubleExtensionSuffixes[] = { "gz", "z", "bz2", "bz" };
-const char* kCommonDoubleExtensions[] = { "user.js" };
+const char* const kCommonDoubleExtensionSuffixes[] = { "gz", "z", "bz2", "bz" };
+const char* const kCommonDoubleExtensions[] = { "user.js" };
 
 const FilePath::CharType kStringTerminator = FILE_PATH_LITERAL('\0');