Use unique_ptr for last_fetch_trigger_type_

Undefined behavior occurs (observed as a crash) when the Feed Internals
page is loaded and the last_fetch_trigger_type_ var is uninitialized,
so wrapping it here in a nullable pointer to avoid this.

Bug: 981513
Change-Id: I8637412423ab14d1a1329a414997d1f38887daaa
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1691046Reviewed-by: Sky Malice <skym@chromium.org>
Commit-Queue: Natalie Chouinard <chouinard@chromium.org>
Cr-Commit-Position: refs/heads/master@{#675698}

chrome/browser/ui/webui/feed_internals/feed_internals_page_handler.cc

@@ -31,8 +31,10 @@ feed_internals::mojom::TimePtr ToMojoTime(base::Time time) {
                         : feed_internals::mojom::Time::New(time.ToJsTime());
 }
 
-std::string TriggerTypeToString(feed::FeedSchedulerHost::TriggerType trigger) {
-  switch (trigger) {
+std::string TriggerTypeToString(feed::FeedSchedulerHost::TriggerType* trigger) {
+  if (trigger == nullptr)
+    return "Not set";
+  switch (*trigger) {
     case feed::FeedSchedulerHost::TriggerType::kNtpShown:
       return "NTP Shown";
     case feed::FeedSchedulerHost::TriggerType::kForegrounded:

components/feed/core/feed_scheduler_host.cc

@@ -507,8 +507,8 @@ int FeedSchedulerHost::GetLastFetchStatusForDebugging() const {
   return last_fetch_status_;
 }
 
-TriggerType FeedSchedulerHost::GetLastFetchTriggerTypeForDebugging() const {
-  return last_fetch_trigger_type_;
+TriggerType* FeedSchedulerHost::GetLastFetchTriggerTypeForDebugging() const {
+  return last_fetch_trigger_type_.get();
 }
 
 void FeedSchedulerHost::OnEulaAccepted() {
@@ -602,7 +602,7 @@ FeedSchedulerHost::ShouldRefreshResult FeedSchedulerHost::ShouldRefresh(
       clock_->Now() +
       base::TimeDelta::FromSeconds(kTimeoutDurationSeconds.Get());
 
-  last_fetch_trigger_type_ = trigger;
+  last_fetch_trigger_type_ = std::make_unique<TriggerType>(trigger);
 
   return kShouldRefresh;
 }

components/feed/core/feed_scheduler_host.h

@@ -146,7 +146,7 @@ class FeedSchedulerHost : web_resource::EulaAcceptedNotifier::Observer {
   // Surface the TriggerType for the last ShouldRefresh check that resulted in
   // kShouldRefresh. Callers of ShouldRefresh are presumed to follow with the
   // actual refresh.
-  TriggerType GetLastFetchTriggerTypeForDebugging() const;
+  TriggerType* GetLastFetchTriggerTypeForDebugging() const;
 
  private:
   FRIEND_TEST_ALL_PREFIXES(FeedSchedulerHostTest, GetTriggerThreshold);
@@ -234,7 +234,7 @@ class FeedSchedulerHost : web_resource::EulaAcceptedNotifier::Observer {
   int last_fetch_status_ = 0;
 
   // Reason for last fetch for debugging.
-  TriggerType last_fetch_trigger_type_;
+  std::unique_ptr<TriggerType> last_fetch_trigger_type_;
 
   DISALLOW_COPY_AND_ASSIGN(FeedSchedulerHost);
 };

components/feed/core/feed_scheduler_host_unittest.cc

@@ -1040,19 +1040,19 @@ TEST_F(FeedSchedulerHostTest, GetLastFetchTriggerTypeForDebugging) {
   scheduler()->OnForegrounded();
 
   EXPECT_EQ(FeedSchedulerHost::TriggerType::kForegrounded,
-            scheduler()->GetLastFetchTriggerTypeForDebugging());
+            *scheduler()->GetLastFetchTriggerTypeForDebugging());
 
   scheduler()->OnArticlesCleared(/*suppress_refreshes*/ false);
 
   EXPECT_EQ(FeedSchedulerHost::TriggerType::kNtpShown,
-            scheduler()->GetLastFetchTriggerTypeForDebugging());
+            *scheduler()->GetLastFetchTriggerTypeForDebugging());
 
   ClassifyAsActiveSuggestionsConsumer();  // Fixed timer at 48 hours.
   test_clock()->Advance(TimeDelta::FromHours(49));
   scheduler()->OnFixedTimer(base::OnceClosure());
 
   EXPECT_EQ(FeedSchedulerHost::TriggerType::kFixedTimer,
-            scheduler()->GetLastFetchTriggerTypeForDebugging());
+            *scheduler()->GetLastFetchTriggerTypeForDebugging());
 }
 
 }  // namespace feed