Speedup function profile by using a hash table instead of a linear scan

runtime/vm/profiler_service.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 VM_PROFILER_SERVICE_H_
 #define VM_PROFILER_SERVICE_H_
 
 #include "vm/allocation.h"
 #include "vm/code_observers.h"
 #include "vm/globals.h"
@@ skipping 55 matching lines @@
                   const Function& function,
                   const intptr_t table_index);
 
   const char* name() const {
     ASSERT(name_ != NULL);
     return name_;
   }
 
   const char* Name() const;
 
-  RawFunction* function() const {
-    return function_.raw();
+  const Function* function() const {
+    return &function_;
   }
 
   intptr_t table_index() const {
     return table_index_;
   }
 
   Kind kind() const {
     return kind_;
   }
 
@@ skipping 376 matching lines @@
                             JSONStream* stream,
                             Profile::TagOrder tag_order,
                             intptr_t extra_tags,
                             SampleFilter* filter,
                             bool as_timline);
 };
 
 }  // namespace dart
 
 #endif  // VM_PROFILER_SERVICE_H_