Reverts CLs related to the TLAB due to heap exhaustion.

runtime/vm/thread.h

 // Copyright (c) 2015, 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.
 
 #ifndef RUNTIME_VM_THREAD_H_
 #define RUNTIME_VM_THREAD_H_
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "vm/atomic.h"
@@ skipping 348 matching lines @@
   void set_top_resource(StackResource* value) { top_resource_ = value; }
   static intptr_t top_resource_offset() {
     return OFFSET_OF(Thread, top_resource_);
   }
 
   // Heap of the isolate that this thread is operating on.
   Heap* heap() const { return heap_; }
   static intptr_t heap_offset() { return OFFSET_OF(Thread, heap_); }
 
   void set_top(uword value) {
+    ASSERT(heap_ != NULL);
     top_ = value;
   }
   void set_end(uword value) {
+    ASSERT(heap_ != NULL);
     end_ = value;
   }
 
   uword top() { return top_; }
   uword end() { return end_; }
 
-  bool HasActiveTLAB() { return end_ > 0; }
-
   static intptr_t top_offset() { return OFFSET_OF(Thread, top_); }
   static intptr_t end_offset() { return OFFSET_OF(Thread, end_); }
 
   int32_t no_handle_scope_depth() const {
 #if defined(DEBUG)
     return no_handle_scope_depth_;
 #else
     return 0;
 #endif
   }
@@ skipping 442 matching lines @@
 // Disable thread interrupts.
 class DisableThreadInterruptsScope : public StackResource {
  public:
   explicit DisableThreadInterruptsScope(Thread* thread);
   ~DisableThreadInterruptsScope();
 };
 
 }  // namespace dart
 
 #endif  // RUNTIME_VM_THREAD_H_