Add ImmutableHeap class consisting of parts

src/vm/object_memory.h

 // Copyright (c) 2014, the Fletch 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.md file.
 
 #ifndef SRC_VM_OBJECT_MEMORY_H_
 #define SRC_VM_OBJECT_MEMORY_H_
 
 #include "src/shared/globals.h"
 #include "src/shared/platform.h"
 #include "src/shared/utils.h"
@@ skipping 54 matching lines @@
   void set_owner(Space* value) { owner_ = value; }
 
   friend class ObjectMemory;
   friend class PageTable;
   friend class Space;
 };
 
 // Space is a chain of chunks. It supports allocation and traversal.
 class Space {
  public:
+  static const int kDefaultChunkSize = 128 * KB;
+
   explicit Space(int maximum_initial_size = 0);
 
   ~Space();
 
   // Allocate raw object.
   uword Allocate(int size);
 
   // Rewind allocation top by size bytes if location is equal to current
   // allocation top.
   void TryDealloc(uword location, int size);
@@ skipping 19 matching lines @@
 
   // Schema change support.
   void CompleteTransformations(PointerVisitor* visitor, Process* process);
 
   // Returns true if the address is inside this space.
   inline bool Includes(uword address) const;
 
   // Adjust the allocation budget based on the current heap size.
   void AdjustAllocationBudget();
 
+  void SetAllocationBudget(int new_budget);
+
   // Tells whether garbage collection is needed.
   bool needs_garbage_collection() { return allocation_budget_ <= 0; }
 
   bool in_no_allocation_failure_scope() { return no_allocation_nesting_ != 0; }
 
   // TODO(kasperl): This seems like a bad interface.
   void AppendProgramChunk(Chunk* chunk, uword top) {
     Append(chunk);
     top_ = top;
     limit_ = chunk->limit_;
   }
 
   // Takes all chunks inside [space] and prepends it to this space.
   // The given [space] will be deleted.
   void PrependSpace(Space* space);
 
   bool is_empty() const { return first_ == NULL; }
 
  private:
   friend class NoAllocationFailureScope;
 
-  static const int kDefaultChunkSize = 128 * KB;
-
   uword TryAllocate(int size);
   uword AllocateInNewChunk(int size);
 
   void Append(Chunk* chunk);
 
   Chunk* first() { return first_; }
   Chunk* last() { return last_; }
   uword top() { return top_; }
 
   void IncrementNoAllocationNesting() { ++no_allocation_nesting_; }
@@ skipping 91 matching lines @@
   friend class Space;
 };
 
 inline bool Space::Includes(uword address) const {
   return ObjectMemory::IsAddressInSpace(address, this);
 }
 
 }  // namespace fletch
 
 #endif  // SRC_VM_OBJECT_MEMORY_H_