Revert "[Dolphin] Add a sequence checker"

This reverts commit bef7a422.

Reason for revert:

Findit (https://goo.gl/kROfz5) identified CL at revision 683057 as the
culprit for failures in the build cycles as shown on:
https://analysis.chromium.org/waterfall/culprit?key=ag9zfmZpbmRpdC1mb3ItbWVyRAsSDVdmU3VzcGVjdGVkQ0wiMWNocm9taXVtL2JlZjdhNDIyZTk4N2U1NTcxYWYxZjZhNWM0MGEzMjQxMzFlNjk3ZDAM

Sample Failed Build: https://ci.chromium.org/buildbot/chromium.memory/Linux%20Chromium%20OS%20ASan%20LSan%20Tests%20%281%29/34678

Sample Failed Step: unit_tests

Original change's description:
> [Dolphin] Add a sequence checker
> 
> The RecurrenceRanker isn't threadsafe, so we should formalize this.
> This CL adds a sequence DCHECK to all public methods (and a couple
> of private callbacks, for clarity).
> 
> Bug: 921444
> Change-Id: Ib52f8e33be82de147efd23e67c424083ff980184
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1729991
> Reviewed-by: Charles . <charleszhao@chromium.org>
> Commit-Queue: Tony Yeoman <tby@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#683057}


Change-Id: Idfac688d72ba6a356259a575209b755ec340b7ac
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 921444
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1730620
Cr-Commit-Position: refs/heads/master@{#683131}

chrome/browser/ui/app_list/search/search_result_ranker/recurrence_ranker.cc

@@ -166,7 +166,6 @@ RecurrenceRanker::RecurrenceRanker(const std::string& model_identifier,
           TimeDelta::FromSeconds(config.min_seconds_between_saves())),
       time_of_last_save_(Time::Now()),
       weak_factory_(this) {
-  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   task_runner_ = base::CreateSequencedTaskRunnerWithTraits(
       {base::TaskPriority::BEST_EFFORT, base::MayBlock(),
        base::TaskShutdownBehavior::SKIP_ON_SHUTDOWN});
@@ -202,7 +201,6 @@ RecurrenceRanker::~RecurrenceRanker() = default;
 
 void RecurrenceRanker::OnLoadProtoFromDiskComplete(
     std::unique_ptr<RecurrenceRankerProto> proto) {
-  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   load_from_disk_completed_ = true;
   LogInitializationStatus(model_identifier_,
                           InitializationStatus::kInitialized);
@@ -244,7 +242,6 @@ void RecurrenceRanker::OnLoadProtoFromDiskComplete(
 
 void RecurrenceRanker::Record(const std::string& target,
                               const std::string& condition) {
-  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   if (!load_from_disk_completed_)
     return;
   LogUsage(model_identifier_, Usage::kRecord);
@@ -255,7 +252,6 @@ void RecurrenceRanker::Record(const std::string& target,
 
 void RecurrenceRanker::RenameTarget(const std::string& target,
                                     const std::string& new_target) {
-  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   if (!load_from_disk_completed_)
     return;
   LogUsage(model_identifier_, Usage::kRenameTarget);
@@ -265,7 +261,6 @@ void RecurrenceRanker::RenameTarget(const std::string& target,
 }
 
 void RecurrenceRanker::RemoveTarget(const std::string& target) {
-  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   // TODO(tby): Find a solution to the edge case of a removal before disk
   // loading is complete, resulting in the remove getting dropped.
   if (!load_from_disk_completed_)
@@ -278,7 +273,6 @@ void RecurrenceRanker::RemoveTarget(const std::string& target) {
 
 void RecurrenceRanker::RenameCondition(const std::string& condition,
                                        const std::string& new_condition) {
-  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   if (!load_from_disk_completed_)
     return;
   LogUsage(model_identifier_, Usage::kRenameCondition);
@@ -288,7 +282,6 @@ void RecurrenceRanker::RenameCondition(const std::string& condition,
 }
 
 void RecurrenceRanker::RemoveCondition(const std::string& condition) {
-  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   if (!load_from_disk_completed_)
     return;
   LogUsage(model_identifier_, Usage::kRemoveCondition);
@@ -299,7 +292,6 @@ void RecurrenceRanker::RemoveCondition(const std::string& condition) {
 
 std::map<std::string, float> RecurrenceRanker::Rank(
     const std::string& condition) {
-  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   if (!load_from_disk_completed_)
     return {};
   LogUsage(model_identifier_, Usage::kRank);
@@ -321,7 +313,6 @@ std::map<std::string, float> RecurrenceRanker::Rank(
 
 void RecurrenceRanker::MaybeCleanup(float proportion_valid,
                                     const FrecencyStore::ScoreTable& targets) {
-  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   if (proportion_valid > kMinValidTargetProportionBeforeCleanup)
     return;
 
@@ -334,7 +325,6 @@ void RecurrenceRanker::MaybeCleanup(float proportion_valid,
 std::vector<std::pair<std::string, float>> RecurrenceRanker::RankTopN(
     int n,
     const std::string& condition) {
-  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   if (!load_from_disk_completed_)
     return {};
 
@@ -343,18 +333,15 @@ std::vector<std::pair<std::string, float>> RecurrenceRanker::RankTopN(
 
 std::map<std::string, FrecencyStore::ValueData>*
 RecurrenceRanker::GetTargetData() {
-  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   return targets_->get_mutable_values();
 }
 
 std::map<std::string, FrecencyStore::ValueData>*
 RecurrenceRanker::GetConditionData() {
-  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   return conditions_->get_mutable_values();
 }
 
 void RecurrenceRanker::SaveToDisk() {
-  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   if (is_ephemeral_user_)
     return;
 
@@ -367,14 +354,12 @@ void RecurrenceRanker::SaveToDisk() {
 }
 
 void RecurrenceRanker::MaybeSave() {
-  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   if (Time::Now() - time_of_last_save_ > min_seconds_between_saves_) {
     SaveToDisk();
   }
 }
 
 void RecurrenceRanker::ToProto(RecurrenceRankerProto* proto) {
-  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   proto->set_config_hash(config_hash_);
   predictor_->ToProto(proto->mutable_predictor());
   targets_->ToProto(proto->mutable_targets());

chrome/browser/ui/app_list/search/search_result_ranker/recurrence_ranker.h

@@ -142,8 +142,6 @@ class RecurrenceRanker {
   const base::TimeDelta min_seconds_between_saves_;
   base::Time time_of_last_save_;
 
-  SEQUENCE_CHECKER(sequence_checker_);
-
   scoped_refptr<base::SequencedTaskRunner> task_runner_;
   base::WeakPtrFactory<RecurrenceRanker> weak_factory_;