Sort the output (for now just the classes and instance members).

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 0b9fca1014c852c45d5715f9bc5717251d906b35..5b7d44a8cf864a98fb83b98061e87280bd83addf 100644
--- a/lib/compiler/implementation/elements/elements.dart
+++ b/lib/compiler/implementation/elements/elements.dart
@@ -96,7 +96,7 @@ class ElementKind {
   toString() => id;
 }
 
-class Element implements Hashable {
+class Element implements Comparable, Hashable {
   final SourceString name;
   final ElementKind kind;
   final Element enclosingElement;
@@ -156,6 +156,23 @@ class Element implements Hashable {
   // the same hash code. Replace this with a simple id in the element?
   int hashCode() => name.hashCode();
 
+  /** Two elements are compared first according to their library name, then
+    * by their position in the source. */
+  int compareTo(Element other) {
+    SourceString lib1Name = this.getLibrary().name;
+    SourceString lib2Name = other.getLibrary().name;
+    int libComparison = lib1Name.compareTo(lib2Name);
+    if (libComparison != 0) return libComparison;
+    SourceString compilationUnitName1 = this.getCompilationUnit().name;
+    SourceString compilationUnitName2 = other.getCompilationUnit().name;
+    int compilationUnitComparison =
+        compilationUnitName1.compareTo(compilationUnitName2);
+    if (compilationUnitComparison != 0) return compilationUnitComparison;
+    int charOffset1 = this.position().charOffset;
+    int charOffset2 = other.position().charOffset;
+    return charOffset1.compareTo(charOffset2);
+  }
+
   CompilationUnitElement getCompilationUnit() {
     Element element = this;
     while (element !== null && !element.isCompilationUnit()) {