Change IllegalArgumentException to ArgumentError.

pkg/dartdoc/lib/src/mirrors/dart2js_mirror.dart

Index: pkg/dartdoc/lib/src/mirrors/dart2js_mirror.dart
diff --git a/pkg/dartdoc/lib/src/mirrors/dart2js_mirror.dart b/pkg/dartdoc/lib/src/mirrors/dart2js_mirror.dart
index e5d0af6f97aa30a23f0ce6b75be2c885cf063dd3..39b1aa168861979ea58fb2381f618a1782adae2b 100644
--- a/pkg/dartdoc/lib/src/mirrors/dart2js_mirror.dart
+++ b/pkg/dartdoc/lib/src/mirrors/dart2js_mirror.dart
@@ -74,7 +74,7 @@ Dart2JsTypeMirror _convertTypeToTypeMirror(
   } else if (type is TypedefType) {
     return new Dart2JsTypedefMirror(system, type);
   }
-  throw new IllegalArgumentException("Unexpected interface type $type");
+  throw new ArgumentError("Unexpected interface type $type");
 }
 
 Collection<Dart2JsMemberMirror> _convertElementMemberToMemberMirrors(
@@ -95,7 +95,7 @@ Collection<Dart2JsMemberMirror> _convertElementMemberToMemberMirrors(
     }
     return members;
   }
-  throw new IllegalArgumentException(
+  throw new ArgumentError(
       "Unexpected member type $element ${element.kind}");
 }
 
@@ -297,7 +297,7 @@ class Dart2JsCompilation implements Compilation {
 
   Future<String> provider(Uri uri) {
     if (uri.scheme != 'file') {
-      throw new IllegalArgumentException(uri);
+      throw new ArgumentError(uri);
     }
     String source;
     try {