Change function source fingerprint calculation to rely on tokens exclusively and

runtime/vm/object.cc

Index: runtime/vm/object.cc
diff --git a/runtime/vm/object.cc b/runtime/vm/object.cc
index 9df1d5ca2786f5ce8fdc71d62fc3bd0434db274c..935712e38766556b92141061855127fe59d94f41 100644
--- a/runtime/vm/object.cc
+++ b/runtime/vm/object.cc
@@ -6751,9 +6751,7 @@ RawString* Function::GetSource() const {
 // Construct fingerprint from token stream. The token stream contains also
 // arguments.
 int32_t Function::SourceFingerprint() const {
-  uint32_t result = IsImplicitClosureFunction()
-      ? String::Handle(Function::Handle(parent_function()).Signature()).Hash()
-      : String::Handle(Signature()).Hash();
+  uint32_t result = 0;
   TokenStream::Iterator tokens_iterator(TokenStream::Handle(
       Script::Handle(script()).tokens()), token_pos());
   Object& obj = Object::Handle();