deps: cherry-pick 676c413 from upstream V8

Original commit message:

    [heap] Fix threshold for delayed chunks after 2c7561.

    Bug: chromium:771966
    Change-Id: Iac5ee55c0d31de477f21f091f4be015a1ca8d00c
    Reviewed-on: https://chromium-review.googlesource.com/702382
    Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
    Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
    Cr-Commit-Position: refs/heads/master@{#48316}

Refs: v8/v8@676c413
Refs: nodejs/help#917 (comment)
Refs: https://bugs.chromium.org/p/chromium/issues/detail?id=771966

PR-URL: #16490
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>

Author: targos

common.gypi

@@ -27,7 +27,7 @@
 
     # Reset this number to 0 on major V8 upgrades.
     # Increment by one for each non-official patch applied to deps/v8.
-    'v8_embedder_string': '-node.5',
+    'v8_embedder_string': '-node.6',
 
     # Enable disassembler for `--print-code` v8 options
     'v8_enable_disassembler': 1,

deps/v8/src/heap/heap.cc

@@ -1887,7 +1887,7 @@ void Heap::Scavenge() {
 
   if (mark_compact_collector()->sweeper().sweeping_in_progress() &&
       memory_allocator_->unmapper()->NumberOfDelayedChunks() >
-          kMaxSemiSpaceSizeInKB / Page::kPageSize) {
+          static_cast<int>(new_space_->MaximumCapacity() / Page::kPageSize)) {
     mark_compact_collector()->EnsureSweepingCompleted();
   }