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

lib/compiler/implementation/elements/elements.dart

Index: lib/compiler/implementation/elements/elements.dart
diff --git a/lib/compiler/implementation/elements/elements.dart b/lib/compiler/implementation/elements/elements.dart
index 12bde397404d3f540ec577175e2f5761b5bcd2f2..337d3f730560d268280727f1750c7271b13be473 100644
--- a/lib/compiler/implementation/elements/elements.dart
+++ b/lib/compiler/implementation/elements/elements.dart
@@ -399,21 +399,21 @@ class CompilationUnitOverrideElement extends Element {
 }
 
 class LibraryElement extends ScopeContainerElement {
+  final Uri uri;
   CompilationUnitElement entryCompilationUnit;
   Link<CompilationUnitElement> compilationUnits =
       const EmptyLink<CompilationUnitElement>();
-
   Link<ScriptTag> tags = const EmptyLink<ScriptTag>();
   ScriptTag libraryTag;
   bool canUseNative = false;
   LibraryElement patch = null;
 
-  LibraryElement(Script script)
-    : super(new SourceString(script.name), ElementKind.LIBRARY, null) {
+  LibraryElement(Script script, [Uri uri])
+    : this.uri = ((uri === null) ? script.uri : uri),
+      super(new SourceString(script.name), ElementKind.LIBRARY, null) {
     entryCompilationUnit = new CompilationUnitElement(script, this);
   }
 
-  Uri get uri() => entryCompilationUnit.script.uri;
 
   bool get isPatched() => patch !== null;
 
@@ -1027,6 +1027,9 @@ class ClassElement extends ScopeContainerElement
 
   Link<Type> allSupertypes;
 
+  // Lazily applied patch of class members.
+  ClassElement patch = null;
+
   ClassElement(SourceString name, Element enclosing, this.id)
     : super(name, ElementKind.CLASS, enclosing);
 
@@ -1040,6 +1043,8 @@ class ClassElement extends ScopeContainerElement
     return type;
   }
 
+  bool get isPatched() => patch != null;
+
   Link<Type> get typeVariables() => type.arguments;
 
   ClassElement ensureResolved(Compiler compiler) {