Fix cpplint errors in locations that are already being checked

webrtc/common_video/h264/profile_level_id.cc

Index: webrtc/common_video/h264/profile_level_id.cc
diff --git a/webrtc/common_video/h264/profile_level_id.cc b/webrtc/common_video/h264/profile_level_id.cc
index f682862ca1a0bdc4e4fddd0100ec7280deac6b84..cd04bb5b3fd454c718a3ec53c3b8ade0a2c30556 100644
--- a/webrtc/common_video/h264/profile_level_id.cc
+++ b/webrtc/common_video/h264/profile_level_id.cc
@@ -47,7 +47,7 @@ constexpr uint8_t ByteMaskString(char c, const char (&str)[9]) {
 // either 0 or 1.
 class BitPattern {
  public:
-  constexpr BitPattern(const char (&str)[9])
+  explicit constexpr BitPattern(const char (&str)[9])
       : mask_(~ByteMaskString('x', str)),
         masked_value_(ByteMaskString('1', str)) {}