Revert "Improve error messages in MirrorSystem.findLibrary."

runtime/lib/mirrors_patch.dart

Index: runtime/lib/mirrors_patch.dart
diff --git a/runtime/lib/mirrors_patch.dart b/runtime/lib/mirrors_patch.dart
index 1534e796d6d3e41b4952784e2b03d765e9730f09..12cbd56915953763ab13a5716bd2b8d220f32ea1 100644
--- a/runtime/lib/mirrors_patch.dart
+++ b/runtime/lib/mirrors_patch.dart
@@ -36,20 +36,6 @@ patch TypeMirror reflectType(Type key) {
 }
 
 patch class MirrorSystem {
-  /* patch */ LibraryMirror findLibrary(Symbol libraryName) {
-    var candidates =
-        libraries.values.where((lib) => lib.simpleName == libraryName);
-    if (candidates.length == 1) {
-      return candidates.single;
-    }
-    if (candidates.length > 1) {
-      var uris = candidates.map((lib) => lib.uri.toString()).toList();
-      throw new Exception("There are multiple libraries named "
-                          "'${getName(libraryName)}': $uris");
-    }
-    throw new Exception("There is no library named '${getName(libraryName)}'");
-  }
-
   /* patch */ static String getName(Symbol symbol) {
     String string = _symbol_dev.Symbol.getName(symbol);