Remove HttpCache::playback_cache_map_

It's not being used.

Bug: None
Change-Id: I527292e7c87e61443b38495ab7f117f391c11e71
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2276249Reviewed-by: Maksim Orlovich <morlovich@chromium.org>
Commit-Queue: Matt Menke <mmenke@chromium.org>
Cr-Commit-Position: refs/heads/master@{#784408}

net/http/http_cache.cc

@@ -419,7 +419,6 @@ void HttpCache::DumpMemoryStats(base::trace_event::ProcessMemoryDump* pmd,
   base::trace_event::MemoryAllocatorDump* dump = pmd->CreateAllocatorDump(name);
   size_t size = base::trace_event::EstimateMemoryUsage(active_entries_) +
                 base::trace_event::EstimateMemoryUsage(doomed_entries_) +
-                base::trace_event::EstimateMemoryUsage(playback_cache_map_) +
                 base::trace_event::EstimateMemoryUsage(pending_ops_);
   if (disk_cache_)
     size += disk_cache_->DumpMemoryStats(pmd, name);

net/http/http_cache.h

@@ -396,7 +396,6 @@ class NET_EXPORT HttpCache : public HttpTransactionFactory {
       std::unordered_map<std::string, std::unique_ptr<ActiveEntry>>;
   using PendingOpsMap = std::unordered_map<std::string, PendingOp*>;
   using ActiveEntriesSet = std::map<ActiveEntry*, std::unique_ptr<ActiveEntry>>;
-  using PlaybackCacheMap = std::unordered_map<std::string, int>;
 
   // Methods ------------------------------------------------------------------
 
@@ -666,8 +665,6 @@ class NET_EXPORT HttpCache : public HttpTransactionFactory {
   // The set of entries "under construction".
   PendingOpsMap pending_ops_;
 
-  std::unique_ptr<PlaybackCacheMap> playback_cache_map_;
-
   // A clock that can be swapped out for testing.
   base::Clock* clock_;