[PM] Get rid of kInvalidVoterId

The IdType class already has built-in support for an invalid ID.

Bug: 971272
Change-Id: I7121400d72c22b90c153da32f0a0f74e46a27569
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2545442
Commit-Queue: Patrick Monette <pmonette@chromium.org>
Reviewed-by: François Doray <fdoray@chromium.org>
Cr-Commit-Position: refs/heads/master@{#833369}

components/performance_manager/execution_context_priority/boosting_vote_aggregator.cc

@@ -248,7 +248,7 @@ BoostingVoteAggregator::~BoostingVoteAggregator() {
 
 VotingChannel BoostingVoteAggregator::GetVotingChannel() {
   DCHECK(nodes_.empty());
-  DCHECK_EQ(voting::kInvalidVoterId<Vote>, input_voter_id_);
+  DCHECK(!input_voter_id_);
   DCHECK_GT(1u, vote_consumer_default_impl_.voting_channels_issued());
   auto channel = vote_consumer_default_impl_.BuildVotingChannel();
   input_voter_id_ = channel.voter_id();
@@ -260,7 +260,7 @@ void BoostingVoteAggregator::SetUpstreamVotingChannel(VotingChannel&& channel) {
 }
 
 bool BoostingVoteAggregator::IsSetup() const {
-  return input_voter_id_ != voting::kInvalidVoterId<Vote> && channel_.IsValid();
+  return input_voter_id_ && channel_.IsValid();
 }
 
 void BoostingVoteAggregator::SubmitBoostingVote(

components/performance_manager/execution_context_priority/boosting_vote_aggregator.h

@@ -367,7 +367,7 @@ class BoostingVoteAggregator : public VoteObserver {
 
   // Our input voter. We'll only accept votes from this voter otherwise we'll
   // DCHECK.
-  voting::VoterId<Vote> input_voter_id_ = voting::kInvalidVoterId<Vote>;
+  voting::VoterId<Vote> input_voter_id_;
 
   // Our channel for upstreaming our votes.
   VotingChannelWrapper channel_;

components/performance_manager/execution_context_priority/execution_context_priority_unittest.cc

@@ -129,7 +129,7 @@ TEST(ExecutionContextPriorityTest, VoteReceiptsWork) {
   voter.SetVotingChannel(consumer.voting_channel_factory_.BuildVotingChannel());
   EXPECT_EQ(&consumer.voting_channel_factory_,
             voter.voting_channel_.factory_for_testing());
-  EXPECT_NE(voting::kInvalidVoterId<Vote>, voter.voting_channel_.voter_id());
+  EXPECT_TRUE(voter.voting_channel_.voter_id());
   EXPECT_TRUE(voter.voting_channel_.IsValid());
 
   voter.EmitVote(kDummyExecutionContext1, base::TaskPriority::LOWEST);

components/performance_manager/execution_context_priority/override_vote_aggregator.cc

@@ -14,7 +14,7 @@ OverrideVoteAggregator::~OverrideVoteAggregator() = default;
 
 VotingChannel OverrideVoteAggregator::GetOverrideVotingChannel() {
   DCHECK(vote_data_map_.empty());
-  DCHECK_EQ(voting::kInvalidVoterId<Vote>, override_voter_id_);
+  DCHECK(!override_voter_id_);
   DCHECK_GT(2u, vote_consumer_default_impl_.voting_channels_issued());
   auto channel = vote_consumer_default_impl_.BuildVotingChannel();
   override_voter_id_ = channel.voter_id();
@@ -23,7 +23,7 @@ VotingChannel OverrideVoteAggregator::GetOverrideVotingChannel() {
 
 VotingChannel OverrideVoteAggregator::GetDefaultVotingChannel() {
   DCHECK(vote_data_map_.empty());
-  DCHECK_EQ(voting::kInvalidVoterId<Vote>, default_voter_id_);
+  DCHECK(!default_voter_id_);
   DCHECK_GT(2u, vote_consumer_default_impl_.voting_channels_issued());
   auto channel = vote_consumer_default_impl_.BuildVotingChannel();
   default_voter_id_ = channel.voter_id();
@@ -35,9 +35,7 @@ void OverrideVoteAggregator::SetUpstreamVotingChannel(VotingChannel&& channel) {
 }
 
 bool OverrideVoteAggregator::IsSetup() const {
-  return override_voter_id_ != voting::kInvalidVoterId<Vote> &&
-         default_voter_id_ != voting::kInvalidVoterId<Vote> &&
-         channel_.IsValid();
+  return override_voter_id_ && default_voter_id_ && channel_.IsValid();
 }
 
 void OverrideVoteAggregator::OnVoteSubmitted(

components/performance_manager/execution_context_priority/override_vote_aggregator.h

@@ -87,8 +87,8 @@ class OverrideVoteAggregator : public VoteObserver {
 
   // Our two input voters. We'll only accept votes from these voters otherwise
   // we'll DCHECK.
-  VoterId override_voter_id_ = voting::kInvalidVoterId<Vote>;
-  VoterId default_voter_id_ = voting::kInvalidVoterId<Vote>;
+  VoterId override_voter_id_;
+  VoterId default_voter_id_;
 
   // Our channel for upstreaming our votes.
   VotingChannelWrapper channel_;

components/performance_manager/execution_context_priority/root_vote_observer.cc

@@ -62,6 +62,7 @@ void RootVoteObserver::OnVoteChanged(VoterId voter_id,
 void RootVoteObserver::OnVoteInvalidated(
     VoterId voter_id,
     const ExecutionContext* execution_context) {
+  DCHECK_EQ(voter_id_, voter_id);
   SetPriorityAndReason(
       execution_context,
       PriorityAndReason(base::TaskPriority::LOWEST,

components/performance_manager/execution_context_priority/root_vote_observer.h

@@ -39,7 +39,7 @@ class RootVoteObserver : public VoteObserver {
   VoteConsumerDefaultImpl vote_consumer_default_impl_;
 
   // The ID of the only voting channel we've vended.
-  voting::VoterId<Vote> voter_id_ = voting::kInvalidVoterId<Vote>;
+  VoterId voter_id_;
 };
 
 }  // namespace execution_context_priority

components/performance_manager/public/voting/voting.h

@@ -106,8 +106,6 @@ class Vote final {
 
 template <typename VoteImpl>
 using VoterId = util::IdTypeU32<VoteImpl>;
-template <typename VoteImpl>
-constexpr VoterId<VoteImpl> kInvalidVoterId;
 
 // A raw vote becomes an AcceptedVote once a VoteConsumer receives and stores
 // it, associating it with a VoterId.
@@ -252,7 +250,7 @@ class AcceptedVote final {
 
   // The ID of the voter that submitted the vote. This is defined by the
   // VoteConsumer.
-  VoterId<VoteImpl> voter_id_ = kInvalidVoterId<VoteImpl>;
+  VoterId<VoteImpl> voter_id_;
 
   const ContextType* context_ = nullptr;
 
@@ -313,7 +311,7 @@ class VotingChannel final {
   // Used to reach back into the factory to decrement the outstanding
   // VotingChannel count, and for routing votes to the consumer.
   VotingChannelFactory<VoteImpl>* factory_ = nullptr;
-  VoterId<VoteImpl> voter_id_ = kInvalidVoterId<VoteImpl>;
+  VoterId<VoteImpl> voter_id_;
 };
 
 // A helper for creating VotingChannels that binds a unique VoterId (and
@@ -662,7 +660,7 @@ AcceptedVote<VoteImpl>::AcceptedVote(VoteConsumer<VoteImpl>* consumer,
       vote_(vote),
       invalidated_(false) {
   DCHECK(consumer_);
-  DCHECK_NE(voter_id_, kInvalidVoterId<VoteImpl>);
+  DCHECK(voter_id_);
   DCHECK(context_);
   DCHECK(vote_.IsValid());
 }
@@ -700,8 +698,7 @@ bool AcceptedVote<VoteImpl>::HasReceipt(
 
 template <class VoteImpl>
 bool AcceptedVote<VoteImpl>::IsValid() const {
-  return consumer_ && voter_id_ != kInvalidVoterId<VoteImpl> &&
-         vote_.IsValid() && !invalidated_;
+  return consumer_ && voter_id_ && vote_.IsValid() && !invalidated_;
 }
 
 template <class VoteImpl>
@@ -776,7 +773,7 @@ void AcceptedVote<VoteImpl>::Take(AcceptedVote<VoteImpl>&& rhs) {
   DCHECK(!receipt_);
 
   consumer_ = std::exchange(rhs.consumer_, nullptr);
-  voter_id_ = std::exchange(rhs.voter_id_, kInvalidVoterId<VoteImpl>);
+  voter_id_ = std::exchange(rhs.voter_id_, VoterId<VoteImpl>());
   context_ = std::exchange(rhs.context_, nullptr);
   vote_ = std::exchange(rhs.vote_, VoteImpl());
   receipt_ = std::exchange(rhs.receipt_, nullptr);
@@ -821,17 +818,17 @@ VoteReceipt<VoteImpl> VotingChannel<VoteImpl>::SubmitVote(
 
 template <class VoteImpl>
 bool VotingChannel<VoteImpl>::IsValid() const {
-  return factory_ && voter_id_ != kInvalidVoterId<VoteImpl>;
+  return factory_ && voter_id_;
 }
 
 template <class VoteImpl>
 void VotingChannel<VoteImpl>::Reset() {
   if (!factory_)
     return;
-  DCHECK_NE(kInvalidVoterId<VoteImpl>, voter_id_);
+  DCHECK(voter_id_);
   factory_->OnVotingChannelDestroyed(PassKey());
   factory_ = nullptr;
-  voter_id_ = kInvalidVoterId<VoteImpl>;
+  voter_id_ = VoterId<VoteImpl>();
 }
 
 template <class VoteImpl>
@@ -845,7 +842,7 @@ template <class VoteImpl>
 void VotingChannel<VoteImpl>::Take(VotingChannel<VoteImpl>&& rhs) {
   Reset();
   factory_ = std::exchange(rhs.factory_, nullptr);
-  voter_id_ = std::exchange(rhs.voter_id_, kInvalidVoterId<VoteImpl>);
+  voter_id_ = std::exchange(rhs.voter_id_, VoterId<VoteImpl>());
 }
 
 /////////////////////////////////////////////////////////////////////
@@ -869,8 +866,12 @@ VotingChannel<VoteImpl> VotingChannelFactory<VoteImpl>::BuildVotingChannel() {
   ++voting_channels_outstanding_;
   // TODO(sebmarchand): Use VoterId<VoteImpl>::Generator instead of
   // FromUnsafeValue.
+  // Note: The pre-increment operator is used so that the value of the first
+  // voter ID is 1. This is required because 0 is the value for an invalid
+  // VoterId.
   VoterId<VoteImpl> new_voter_id =
       VoterId<VoteImpl>::FromUnsafeValue(++voting_channels_issued_);
+  DCHECK(!new_voter_id.is_null());
   return VotingChannel<VoteImpl>(
       base::PassKey<VotingChannelFactory<VoteImpl>>(), this, new_voter_id);
 }

components/performance_manager/voting_unittest.cc

@@ -71,8 +71,7 @@ TEST(VotingTest, VoteReceiptsWork) {
   voter.SetVotingChannel(consumer.voting_channel_factory_.BuildVotingChannel());
   EXPECT_EQ(&consumer.voting_channel_factory_,
             voter.voting_channel_.factory_for_testing());
-  EXPECT_NE(voting::kInvalidVoterId<TestVote>,
-            voter.voting_channel_.voter_id());
+  EXPECT_TRUE(voter.voting_channel_.voter_id());
   EXPECT_TRUE(voter.voting_channel_.IsValid());
 
   voter.EmitVote(kDummyContext1, 0);