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

runtime/vm/scopes.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_SCOPES_H_
 #define VM_SCOPES_H_
 
 #include "platform/assert.h"
 #include "platform/globals.h"
 #include "vm/allocation.h"
@@ skipping 261 matching lines @@
   SourceLabel* LookupLabel(const String& name);
 
   // Lookup the "innermost" label that labels a for, while, do, or switch
   // statement.
   SourceLabel* LookupInnermostLabel(Token::Kind jump_kind);
 
   // Lookup scope of outer switch statement at same function level.
   // 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
   // outer scope of a switch statement. If there is no outer switch
   // statement, return the first unresolved label found.
   SourceLabel* CheckUnresolvedLabels();
 
   // Accessing the variables in the scope.
   intptr_t num_variables() const { return variables_.length(); }
   LocalVariable* VariableAt(intptr_t index) const {
@@ skipping 26 matching lines @@
                         bool* found_captured_variables);
 
   // Creates variable info for the scope and all its nested scopes.
   // Must be called after AllocateVariables() has been called.
   RawLocalVarDescriptors* GetVarDescriptors(const Function& func);
 
   // Create a ContextScope object describing all captured variables referenced
   // 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();
 
   // Creates a LocalScope representing the outer scope of a local function to be
   // compiled. This outer scope contains the variables captured by the function
   // as specified by the given ContextScope, which was created during the
   // compilation of the enclosing function.
   static LocalScope* RestoreOuterScope(const ContextScope& context_scope);
 
@@ skipping 35 matching lines @@
   // List of names referenced in this scope and its children that
   // are not resolved to local variables.
   GrowableArray<NameReference*> referenced_;
 
   DISALLOW_COPY_AND_ASSIGN(LocalScope);
 };
 
 }  // namespace dart
 
 #endif  // VM_SCOPES_H_