base: Sprinkle constexpr/noexcept on Token methods.

Change-Id: I94dbcfd3e5114b23433900397ec023c5d7513545
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2281551
Commit-Queue: Victor Costan <pwnall@chromium.org>
Reviewed-by: danakj <danakj@chromium.org>
Cr-Commit-Position: refs/heads/master@{#786152}

base/token.h

@@ -7,7 +7,7 @@
 
 #include <stdint.h>
 
-#include <iosfwd>
+#include <string>
 #include <tuple>
 
 #include "base/base_export.h"
@@ -25,28 +25,35 @@ namespace base {
 class BASE_EXPORT Token {
  public:
   // Constructs a zero Token.
-  constexpr Token() : high_(0), low_(0) {}
+  constexpr Token() = default;
 
   // Constructs a Token with |high| and |low| as its contents.
   constexpr Token(uint64_t high, uint64_t low) : high_(high), low_(low) {}
 
+  constexpr Token(const Token&) = default;
+  constexpr Token& operator=(const Token&) = default;
+  constexpr Token(Token&&) noexcept = default;
+  constexpr Token& operator=(Token&&) = default;
+
   // Constructs a new Token with random |high| and |low| values taken from a
   // cryptographically strong random source.
   static Token CreateRandom();
 
   // The high and low 64 bits of this Token.
-  uint64_t high() const { return high_; }
-  uint64_t low() const { return low_; }
+  constexpr uint64_t high() const { return high_; }
+  constexpr uint64_t low() const { return low_; }
 
-  bool is_zero() const { return high_ == 0 && low_ == 0; }
+  constexpr bool is_zero() const { return high_ == 0 && low_ == 0; }
 
-  bool operator==(const Token& other) const {
+  constexpr bool operator==(const Token& other) const {
     return high_ == other.high_ && low_ == other.low_;
   }
 
-  bool operator!=(const Token& other) const { return !(*this == other); }
+  constexpr bool operator!=(const Token& other) const {
+    return !(*this == other);
+  }
 
-  bool operator<(const Token& other) const {
+  constexpr bool operator<(const Token& other) const {
     return std::tie(high_, low_) < std::tie(other.high_, other.low_);
   }
 
@@ -57,8 +64,8 @@ class BASE_EXPORT Token {
   // Note: Two uint64_t are used instead of uint8_t[16] in order to have a
   // simpler implementation, paricularly for |ToString()|, |is_zero()|, and
   // constexpr value construction.
-  uint64_t high_;
-  uint64_t low_;
+  uint64_t high_ = 0;
+  uint64_t low_ = 0;
 };
 
 // For use in std::unordered_map.

base/unguessable_token.h

@@ -66,6 +66,11 @@ class BASE_EXPORT UnguessableToken {
   // Assign to it with Create() before using it.
   constexpr UnguessableToken() = default;
 
+  constexpr UnguessableToken(const UnguessableToken&) = default;
+  constexpr UnguessableToken& operator=(const UnguessableToken&) = default;
+  constexpr UnguessableToken(UnguessableToken&&) noexcept = default;
+  constexpr UnguessableToken& operator=(UnguessableToken&&) = default;
+
   // NOTE: Serializing an empty UnguessableToken is an illegal operation.
   uint64_t GetHighForSerialization() const {
     DCHECK(!is_empty());
@@ -78,22 +83,22 @@ class BASE_EXPORT UnguessableToken {
     return token_.low();
   }
 
-  bool is_empty() const { return token_.is_zero(); }
+  constexpr bool is_empty() const { return token_.is_zero(); }
 
   // Hex representation of the unguessable token.
   std::string ToString() const { return token_.ToString(); }
 
-  explicit operator bool() const { return !is_empty(); }
+  explicit constexpr operator bool() const { return !is_empty(); }
 
-  bool operator<(const UnguessableToken& other) const {
+  constexpr bool operator<(const UnguessableToken& other) const {
     return token_ < other.token_;
   }
 
-  bool operator==(const UnguessableToken& other) const {
+  constexpr bool operator==(const UnguessableToken& other) const {
     return token_ == other.token_;
   }
 
-  bool operator!=(const UnguessableToken& other) const {
+  constexpr bool operator!=(const UnguessableToken& other) const {
     return !(*this == other);
   }