Make top-level patch injections be compilation unit under library.

lib/compiler/implementation/scanner/listener.dart

Index: lib/compiler/implementation/scanner/listener.dart
diff --git a/lib/compiler/implementation/scanner/listener.dart b/lib/compiler/implementation/scanner/listener.dart
index 18c0442b725a8e2b19a8a0e57c37a21da12a0242..54d68f9e7e892626ee5cadaa9b3a0b5e34edfadb 100644
--- a/lib/compiler/implementation/scanner/listener.dart
+++ b/lib/compiler/implementation/scanner/listener.dart
@@ -547,6 +547,13 @@ class ElementListener extends Listener {
     return node;
   }
 
+  bool allowScriptTags() {
+    // Script tags are only allowed in the library file itself, not in
+    // sourced files.
+    LibraryElement library = compilationUnitElement.getLibrary();
+    return library.entryCompilationUnit == compilationUnitElement;
+  }
+
   void endScriptTag(bool hasPrefix, Token beginToken, Token endToken) {
     StringNode prefix = null;
     Identifier argumentName = null;
@@ -556,14 +563,13 @@ class ElementListener extends Listener {
     }
     StringNode firstArgument = popLiteralString();
     Identifier tag = popNode();
-    LibraryElement library = compilationUnitElement.getLibrary();
-    if (library.entryCompilationUnit != compilationUnitElement) {
+    if (!allowScriptTags()) {
       // Only allow script tags in the entry compilation unit.
       listener.cancel("script tags not allowed here", node: tag);
     }
     ScriptTag scriptTag = new ScriptTag(tag, firstArgument, argumentName,
                                         prefix, beginToken, endToken);
-    library.addTag(scriptTag, listener);
+    addScriptTag(scriptTag);
   }
 
   void endClassDeclaration(int interfacesCount, Token beginToken,
@@ -792,6 +798,10 @@ class ElementListener extends Listener {
     compilationUnitElement.addMember(element, listener);
   }
 
+  void addScriptTag(ScriptTag tag) {
+    compilationUnitElement.getLibrary().addTag(tag, listener);
+  }
+
   void pushNode(Node node) {
     nodes = nodes.prepend(node);
     if (VERBOSE) log("push $nodes");