Add != operator for AccountManager::AccountKey

Also add a note about AccountManager::UpsertToken being idempotent.

Bug: 904128
Bug: 820046
Change-Id: Ie9cc135edf2afad2d9da3c13df5fbc6fc822c4ad
Reviewed-on: https://chromium-review.googlesource.com/c/1349224Reviewed-by: Drew Wilson <atwilson@chromium.org>
Commit-Queue: Kush Sinha <sinhak@chromium.org>
Cr-Commit-Position: refs/heads/master@{#610606}

chromeos/account_manager/account_manager.cc

@@ -161,6 +161,10 @@ bool AccountManager::AccountKey::operator==(const AccountKey& other) const {
   return id == other.id && account_type == other.account_type;
 }
 
+bool AccountManager::AccountKey::operator!=(const AccountKey& other) const {
+  return !(*this == other);
+}
+
 AccountManager::Observer::Observer() = default;
 
 AccountManager::Observer::~Observer() = default;

chromeos/account_manager/account_manager.h

@@ -50,6 +50,7 @@ class CHROMEOS_EXPORT AccountManager {
 
     bool operator<(const AccountKey& other) const;
     bool operator==(const AccountKey& other) const;
+    bool operator!=(const AccountKey& other) const;
   };
 
   // A map from |AccountKey| to a raw token.
@@ -121,6 +122,7 @@ class CHROMEOS_EXPORT AccountManager {
 
   // Updates or inserts a token, for the account corresponding to the given
   // |account_key|. |account_key| must be valid (|AccountKey::IsValid|).
+  // This API is idempotent.
   void UpsertToken(const AccountKey& account_key, const std::string& token);
 
   // Add a non owning pointer to an |AccountManager::Observer|.