Move compilation queues into BackgroundCompiler class

runtime/vm/compiler.h

Index: runtime/vm/compiler.h
diff --git a/runtime/vm/compiler.h b/runtime/vm/compiler.h
index 88b53d57fc3f6b0db546a4730c23685a21063896..fe7f7e96c3b7b5a64486f1c83f0c66ec3cdbf4f8 100644
--- a/runtime/vm/compiler.h
+++ b/runtime/vm/compiler.h
@@ -173,9 +173,14 @@ class BackgroundCompiler : public ThreadPool::Task {
     function_queue_length_ = value;
   }
 
+  void VisitPointers(ObjectPointerVisitor* visitor);
+
  private:
   explicit BackgroundCompiler(Isolate* isolate);
 
+  void set_compilation_function_queue(const GrowableObjectArray& value);
+  void set_compilation_result_queue(const GrowableObjectArray& value);
+
   GrowableObjectArray* FunctionsQueue() const;
   GrowableObjectArray* ResultQueue() const;
 
@@ -196,6 +201,9 @@ class BackgroundCompiler : public ThreadPool::Task {
   // Lightweight access to length of compiler queue.
   intptr_t function_queue_length_;
 
+  RawGrowableObjectArray* compilation_function_queue_;
+  RawGrowableObjectArray* compilation_result_queue_;
+
   DISALLOW_IMPLICIT_CONSTRUCTORS(BackgroundCompiler);
 };