[heap] Check incremental marking limit only on the main thread.

Change-Id: I62e3ad6dc294b575d2b50a68d7dd7c8167fa517d
Reviewed-on: https://chromium-review.googlesource.com/637309
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47655}

src/heap/spaces.cc

@@ -2891,8 +2891,10 @@ HeapObject* FreeList::Allocate(size_t size_in_bytes) {
   // if it is big enough.
   owner_->EmptyAllocationInfo();
 
+  if (!owner_->is_local()) {
     owner_->heap()->StartIncrementalMarkingIfAllocationLimitIsReached(
         Heap::kNoGCFlags, kGCCallbackScheduleIdleGarbageCollection);
+  }
 
   size_t new_node_size = 0;
   FreeSpace* new_node = FindNodeFor(size_in_bytes, &new_node_size);