deps: cherry-pick e0d64dc from upstream V8

Original commit message:

    [heap] Print the number of chunks in unmapper queue in --trace-gc-nvp

    Bug: chromium:771966
    Change-Id: I146b279c4713b7dd716c6d55ca5e6c6e23a3ad7e
    Reviewed-on: https://chromium-review.googlesource.com/704740
    Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
    Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
    Cr-Commit-Position: refs/heads/master@{#48338}

Refs: v8/v8@e0d64dc
Refs: nodejs/help#917 (comment)
Refs: https://bugs.chromium.org/p/chromium/issues/detail?id=771966

PR-URL: #16490
Backport-PR-URL: #16413
Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Ali Ijaz Sheikh <ofrobots@google.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>

deps/v8/src/heap/gc-tracer.cc

@@ -490,6 +490,8 @@ void GCTracer::PrintNVP() const {
           "promotion_rate=%.1f%% "
           "semi_space_copy_rate=%.1f%% "
           "new_space_allocation_throughput=%.1f "
+          "unmapper_chunks=%d "
+          "unmapper_delayed_chunks=%d "
           "context_disposal_rate=%.1f\n",
           duration, spent_in_mutator, current_.TypeName(true),
           current_.reduce_memory, current_.scopes[Scope::HEAP_PROLOGUE],
@@ -520,6 +522,8 @@ void GCTracer::PrintNVP() const {
           AverageSurvivalRatio(), heap_->promotion_rate_,
           heap_->semi_space_copied_rate_,
           NewSpaceAllocationThroughputInBytesPerMillisecond(),
+          heap_->memory_allocator()->unmapper()->NumberOfChunks(),
+          heap_->memory_allocator()->unmapper()->NumberOfDelayedChunks(),
           ContextDisposalRateInMilliseconds());
       break;
     case Event::MINOR_MARK_COMPACTOR:
@@ -654,6 +658,8 @@ void GCTracer::PrintNVP() const {
           "promotion_rate=%.1f%% "
           "semi_space_copy_rate=%.1f%% "
           "new_space_allocation_throughput=%.1f "
+          "unmapper_chunks=%d "
+          "unmapper_delayed_chunks=%d "
           "context_disposal_rate=%.1f "
           "compaction_speed=%.f\n",
           duration, spent_in_mutator, current_.TypeName(true),
@@ -731,6 +737,8 @@ void GCTracer::PrintNVP() const {
           AverageSurvivalRatio(), heap_->promotion_rate_,
           heap_->semi_space_copied_rate_,
           NewSpaceAllocationThroughputInBytesPerMillisecond(),
+          heap_->memory_allocator()->unmapper()->NumberOfChunks(),
+          heap_->memory_allocator()->unmapper()->NumberOfDelayedChunks(),
           ContextDisposalRateInMilliseconds(),
           CompactionSpeedInBytesPerMillisecond());
       break;

deps/v8/src/heap/spaces.cc

@@ -408,6 +408,15 @@ void MemoryAllocator::Unmapper::ReconsiderDelayedChunks() {
   }
 }
 
+int MemoryAllocator::Unmapper::NumberOfChunks() {
+  base::LockGuard<base::Mutex> guard(&mutex_);
+  size_t result = 0;
+  for (int i = 0; i < kNumberOfChunkQueues; i++) {
+    result += chunks_[i].size();
+  }
+  return static_cast<int>(result);
+}
+
 bool MemoryAllocator::CanFreeMemoryChunk(MemoryChunk* chunk) {
   MarkCompactCollector* mc = isolate_->heap()->mark_compact_collector();
   // We cannot free a memory chunk in new space while the sweeper is running

deps/v8/src/heap/spaces.h

@@ -1204,6 +1204,8 @@ class V8_EXPORT_PRIVATE MemoryAllocator {
       return static_cast<int>(delayed_regular_chunks_.size());
     }
 
+    int NumberOfChunks();
+
    private:
     static const int kReservedQueueingSlots = 64;
     static const int kMaxUnmapperTasks = 24;