Remove some duplication in code that extracts the source for a function.

runtime/vm/object.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_OBJECT_H_
 #define VM_OBJECT_H_
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "platform/utils.h"
@@ skipping 1691 matching lines @@
 
 class Function : public Object {
  public:
   RawString* name() const { return raw_ptr()->name_; }
   RawString* PrettyName() const;
   RawString* UserVisibleName() const;
   RawString* QualifiedPrettyName() const;
   RawString* QualifiedUserVisibleName() const;
   virtual RawString* DictionaryName() const { return name(); }
 
-  RawString* GetSource();
+  RawString* GetSource() const;
 
   // Build a string of the form 'C<T, R>(T, {b: B, c: C}) => R' representing the
   // internal signature of the given function. In this example, T and R are
   // type parameters of class C, the owner of the function.
   RawString* Signature() const {
     const bool instantiate = false;
     return BuildSignature(instantiate, kInternalName, TypeArguments::Handle());
   }
 
   RawString* PrettySignature() const {
@@ skipping 1060 matching lines @@
   const char* GetKindAsCString() const;
   intptr_t line_offset() const { return raw_ptr()->line_offset_; }
   intptr_t col_offset() const { return raw_ptr()->col_offset_; }
 
   RawTokenStream* tokens() const { return raw_ptr()->tokens_; }
 
   void Tokenize(const String& private_key) const;
 
   RawLibrary* FindLibrary() const;
   RawString* GetLine(intptr_t line_number) const;
-  RawString* GetSnippet(intptr_t from_token_pos,
-                        intptr_t to_token_pos) const;
   RawString* GetSnippet(intptr_t from_line,
                         intptr_t from_column,
                         intptr_t to_line,
                         intptr_t to_column) const;
 
   void SetLocationOffset(intptr_t line_offset, intptr_t col_offset) const;
 
   void GetTokenLocation(intptr_t token_pos,
                         intptr_t* line, intptr_t* column) const;
 
@@ skipping 5032 matching lines @@
 
 
 RawObject* MegamorphicCache::GetTargetFunction(const Array& array,
                                                intptr_t index) {
   return array.At((index * kEntryLength) + kTargetFunctionIndex);
 }
 
 }  // namespace dart
 
 #endif  // VM_OBJECT_H_