[heap] Remove GlobalSafepoint::Start() and End() methods

Methods are now fully replaced with SafepointScope and are not supposed
to be used anymore.

Bug: v8:10315
Change-Id: I16f9c37b1849590d74fa55c92b8ea5cc83cd7cce
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2413256
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69933}

src/heap/safepoint.cc

@@ -16,10 +16,6 @@ namespace internal {
 GlobalSafepoint::GlobalSafepoint(Heap* heap)
     : heap_(heap), local_heaps_head_(nullptr), active_safepoint_scopes_(0) {}
 
-void GlobalSafepoint::Start() { EnterSafepointScope(); }
-
-void GlobalSafepoint::End() { LeaveSafepointScope(); }
-
 void GlobalSafepoint::EnterSafepointScope() {
   if (!FLAG_local_heaps) return;
 

src/heap/safepoint.h

@@ -43,10 +43,6 @@ class GlobalSafepoint {
     }
   }
 
-  // Use these methods now instead of the more intrusive SafepointScope
-  void Start();
-  void End();
-
   bool IsActive() { return active_safepoint_scopes_ > 0; }
 
  private: