Revert of [heap] Parallel newspace evacuation, semispace copy, and compaction \o/

src/heap/array-buffer-tracker.cc

Index: src/heap/array-buffer-tracker.cc
diff --git a/src/heap/array-buffer-tracker.cc b/src/heap/array-buffer-tracker.cc
index 6e389c1cbf6abe216c782bae30fedcba5b283443..bbe3c6b93679324f90eaa037bbd6e8b71bde07cf 100644
--- a/src/heap/array-buffer-tracker.cc
+++ b/src/heap/array-buffer-tracker.cc
@@ -77,7 +77,6 @@
 
 
 void ArrayBufferTracker::MarkLive(JSArrayBuffer* buffer) {
-  base::LockGuard<base::Mutex> guard(&mutex_);
   void* data = buffer->backing_store();
 
   // ArrayBuffer might be in the middle of being constructed.
@@ -124,8 +123,6 @@
 
 
 void ArrayBufferTracker::Promote(JSArrayBuffer* buffer) {
-  base::LockGuard<base::Mutex> guard(&mutex_);
-
   if (buffer->is_external()) return;
   void* data = buffer->backing_store();
   if (!data) return;