Implement cascade operator in VM

runtime/vm/parser.h

Index: runtime/vm/parser.h
===================================================================
--- runtime/vm/parser.h	(revision 9834)
+++ runtime/vm/parser.h	(working copy)
@@ -414,11 +414,15 @@
   LiteralNode* ParseConstExpr();
   static const bool kRequireConst = true;
   static const bool kAllowConst = false;
-  AstNode* ParseExpr(bool require_compiletime_const);
+  static const bool kConsumeCascades = true;
+  static const bool kNoCascades = false;
+  AstNode* ParseExpr(bool require_compiletime_const, bool consume_cascades);
   AstNode* ParseExprList();
   AstNode* ParseConditionalExpr();
   AstNode* ParseUnaryExpr();
   AstNode* ParsePostfixExpr();
+  AstNode* ParseSelectors(AstNode* primary, bool is_cascade);
+  AstNode* ParseCascades(AstNode* expr);
   AstNode* ParsePrimary();
   AstNode* ParseStringLiteral();
   String* ParseImportStringLiteral();
@@ -440,12 +444,14 @@
   AstNode* ParseInstanceCall(AstNode* receiver, const String& method_name);
   AstNode* ParseClosureCall(AstNode* closure);
   AstNode* ParseInstanceFieldAccess(AstNode* receiver,
-                                    const String& field_name);
+                                    const String& field_name,
+                                    bool consume_cascades);
   AstNode* GenerateStaticFieldLookup(const Field& field,
                                      intptr_t ident_pos);
   AstNode* ParseStaticFieldAccess(const Class& cls,
                                   const String& field_name,
-                                  intptr_t ident_pos);
+                                  intptr_t ident_pos,
+                                  bool consume_cascades);
 
   LocalVariable* LookupLocalScope(const String& ident);
   void CheckInstanceFieldAccess(intptr_t field_pos, const String& field_name);