Roll Observatory packages and add a roll script

packages/analyzer/lib/src/generated/visitors.dart

Index: packages/analyzer/lib/src/generated/visitors.dart
diff --git a/analyzer/lib/src/generated/visitors.dart b/packages/analyzer/lib/src/generated/visitors.dart
similarity index 99%
rename from analyzer/lib/src/generated/visitors.dart
rename to packages/analyzer/lib/src/generated/visitors.dart
index defb317c49229960b98bf433e5b0b3c719d323ae..59e644f37c18f511fe4d3ef9373b12d89c448669 100644
--- a/analyzer/lib/src/generated/visitors.dart
+++ b/packages/analyzer/lib/src/generated/visitors.dart
@@ -303,6 +303,7 @@ class DelegatingAstVisitor<T> implements AstVisitor<T> {
     node.visitChildren(this);
     return null;
   }
+
   @override
   T visitFunctionDeclaration(FunctionDeclaration node) {
     _delegates.forEach((delegate) => delegate.visitFunctionDeclaration(node));
@@ -475,6 +476,7 @@ class DelegatingAstVisitor<T> implements AstVisitor<T> {
     node.visitChildren(this);
     return null;
   }
+
   @override
   T visitMethodInvocation(MethodInvocation node) {
     _delegates.forEach((delegate) => delegate.visitMethodInvocation(node));
@@ -545,6 +547,7 @@ class DelegatingAstVisitor<T> implements AstVisitor<T> {
     node.visitChildren(this);
     return null;
   }
+
   @override
   T visitPrefixedIdentifier(PrefixedIdentifier node) {
     _delegates.forEach((delegate) => delegate.visitPrefixedIdentifier(node));