Migrate most uses of StackZone(Isolate*) to Thread*.

runtime/vm/scavenger.cc

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/scavenger.h"
 
 #include <algorithm>
 #include <map>
 #include <utility>
 
@@ skipping 803 matching lines @@
   }
 
   // Prepare for a scavenge.
   SpaceUsage usage_before = GetCurrentUsage();
   intptr_t promo_candidate_words =
       (survivor_end_ - FirstObjectStart()) / kWordSize;
   Prologue(isolate, invoke_api_callbacks);
   // The API prologue/epilogue may create/destroy zones, so we must not
   // depend on zone allocations surviving beyond the epilogue callback.
   {
-    StackZone zone(isolate);
+    StackZone zone(Thread::Current());
     // Setup the visitor and run the scavenge.
     ScavengerVisitor visitor(isolate, this);
     page_space->AcquireDataLock();
     const bool prologue_weak_are_strong = !invoke_api_callbacks;
     IterateRoots(isolate, &visitor, prologue_weak_are_strong);
     int64_t start = OS::GetCurrentTimeMicros();
     ProcessToSpace(&visitor);
     int64_t middle = OS::GetCurrentTimeMicros();
     IterateWeakReferences(isolate, &visitor);
     ScavengerWeakVisitor weak_visitor(this, prologue_weak_are_strong);
@@ skipping 68 matching lines @@
 }
 
 
 void Scavenger::FreeExternal(intptr_t size) {
   ASSERT(size >= 0);
   external_size_ -= size;
   ASSERT(external_size_ >= 0);
 }
 
 }  // namespace dart