More work for background compilation; move pending_functions_ from ObjectStore to Thread.

runtime/vm/compiler.h

 // Copyright (c) 2012, 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 VM_COMPILER_H_
 #define VM_COMPILER_H_
 
 #include "vm/allocation.h"
 #include "vm/growable_array.h"
 #include "vm/runtime_entry.h"
@@ skipping 101 matching lines @@
 
   void CompileOptimized(const Function& function);
 
  private:
   explicit BackgroundCompiler(Isolate* isolate);
 
   virtual void Run();
 
   void Add(const Function& f) const;
   RawFunction* RemoveOrNull() const;
+  RawFunction* LastOrNull() const;
 
   Isolate* isolate_;
-  bool running_;
-  bool* done_;
-  Monitor* monitor_;
-  Monitor* done_monitor_;
+  bool running_;       // While true, will try to read queue and compile.
+  bool* done_;         // True if the thread is done.
+  Monitor* queue_monitor_;  // Controls access to the queue.
+  Monitor* done_monitor_;   // Notify/wait that the thread is done.
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(BackgroundCompiler);
 };
 
 }  // namespace dart
 
 #endif  // VM_COMPILER_H_