Remove code for expired HttpCache.CantConditionalizeZeroFreshnessFromMemHint

Fixed: 1037125
Change-Id: Id68245046250dd1263ea2e57f6c9dc000e20c5ee
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2359574Reviewed-by: Josh Karlin <jkarlin@chromium.org>
Commit-Queue: Maksim Orlovich <morlovich@chromium.org>
Cr-Commit-Position: refs/heads/master@{#799099}

net/http/http_cache_transaction.cc

@@ -188,7 +188,6 @@ HttpCache::Transaction::Transaction(RequestPriority priority, HttpCache* cache)
       shared_writing_error_(OK),
       cache_entry_status_(CacheEntryStatus::ENTRY_UNDEFINED),
       validation_cause_(VALIDATION_CAUSE_UNDEFINED),
-      cant_conditionalize_zero_freshness_from_memhint_(false),
       recorded_histograms_(false),
       parallel_writing_pattern_(PARALLEL_WRITING_NONE),
       moved_network_transaction_to_writers_(false),
@@ -1130,7 +1129,6 @@ int HttpCache::Transaction::DoOpenOrCreateEntry() {
     // below --- as we've already dropped the old entry.
     couldnt_conditionalize_request_ = true;
     validation_cause_ = VALIDATION_CAUSE_ZERO_FRESHNESS;
-    cant_conditionalize_zero_freshness_from_memhint_ = true;
     UpdateCacheEntryStatus(CacheEntryStatus::ENTRY_CANT_CONDITIONALIZE);
   }
 
@@ -3494,11 +3492,6 @@ void HttpCache::Transaction::RecordHistograms() {
   if (cache_entry_status_ == CacheEntryStatus::ENTRY_CANT_CONDITIONALIZE) {
     UMA_HISTOGRAM_ENUMERATION("HttpCache.CantConditionalizeCause",
                               validation_cause_, VALIDATION_CAUSE_MAX);
-    if (validation_cause_ == VALIDATION_CAUSE_ZERO_FRESHNESS) {
-      UMA_HISTOGRAM_BOOLEAN(
-          "HttpCache.CantConditionalizeZeroFreshnessFromMemHint",
-          cant_conditionalize_zero_freshness_from_memhint_);
-    }
   }
 
   if (cache_entry_status_ == CacheEntryStatus::ENTRY_OTHER)

net/http/http_cache_transaction.h

@@ -645,7 +645,6 @@ class NET_EXPORT_PRIVATE HttpCache::Transaction : public HttpTransaction {
   base::TimeTicks send_request_since_;
   base::TimeTicks read_headers_since_;
   base::Time open_entry_last_used_;
-  bool cant_conditionalize_zero_freshness_from_memhint_;
   bool recorded_histograms_;
   ParallelWritingPattern parallel_writing_pattern_;