Improve async code in VM by not unnecessarily capturing parameters of async and

runtime/vm/scopes.h

Index: runtime/vm/scopes.h
diff --git a/runtime/vm/scopes.h b/runtime/vm/scopes.h
index bc6d2631f2006fbd30e8a1b092cc68b7ff209f82..b9a2b1a4b56dde6316e365a9a9d2754664c79238 100644
--- a/runtime/vm/scopes.h
+++ b/runtime/vm/scopes.h
@@ -279,10 +279,8 @@ class LocalScope : public ZoneAllocated {
   // Returns NULL if this scope is not embedded in a switch.
   LocalScope* LookupSwitchScope();
 
-  // Looks up variable in this scope and mark as captured if applicable.
-  // Finds the variable even if it is marked invisible. Returns true if
-  // the variable was found, false if it was not found.
-  bool CaptureVariable(const String& name);
+  // Mark this variable as captured by this scope.
+  void CaptureVariable(LocalVariable* variable);
 
   // Look for unresolved forward references to labels in this scope.
   // If there are any, propagate the forward reference to the next
@@ -329,7 +327,6 @@ class LocalScope : public ZoneAllocated {
   // from this scope and belonging to outer scopes.
   RawContextScope* PreserveOuterScope(int current_context_level) const;
 
-
   // Recursively traverses all siblings and children and marks all variables as
   // captured.
   void RecursivelyCaptureAllVariables();