Remove NullPointerException.

sdk/lib/_internal/compiler/implementation/lib/interceptors.dart

Index: sdk/lib/_internal/compiler/implementation/lib/interceptors.dart
diff --git a/sdk/lib/_internal/compiler/implementation/lib/interceptors.dart b/sdk/lib/_internal/compiler/implementation/lib/interceptors.dart
index 1f00319e21612daee86dabc0abb3b58b85188bdf..c07d16f48f2939e91c3d83417ff4a59f3316a519 100644
--- a/sdk/lib/_internal/compiler/implementation/lib/interceptors.dart
+++ b/sdk/lib/_internal/compiler/implementation/lib/interceptors.dart
@@ -74,7 +74,6 @@ get$length(var receiver) {
 
 set$length(receiver, newLength) {
   if (isJsArray(receiver)) {
-    checkNull(newLength); // TODO(ahe): This is not specified but co19 tests it.
     if (newLength is !int) throw new ArgumentError(newLength);
     if (newLength < 0) throw new RangeError.value(newLength);
     checkGrowable(receiver, 'set length');
@@ -200,8 +199,6 @@ getRange(receiver, start, length) {
     return UNINTERCEPTED(receiver.getRange(start, length));
   }
   if (0 == length) return [];
-  checkNull(start); // TODO(ahe): This is not specified but co19 tests it.
-  checkNull(length); // TODO(ahe): This is not specified but co19 tests it.
   if (start is !int) throw new ArgumentError(start);
   if (length is !int) throw new ArgumentError(length);
   if (length < 0) throw new ArgumentError(length);
@@ -220,7 +217,6 @@ indexOf$1(receiver, element) {
     var length = JS('num', r'#.length', receiver);
     return Arrays.indexOf(receiver, element, 0, length);
   } else if (receiver is String) {
-    checkNull(element);
     if (element is !String) throw new ArgumentError(element);
     return JS('int', r'#.indexOf(#)', receiver, element);
   }
@@ -233,7 +229,6 @@ indexOf$2(receiver, element, start) {
     var length = JS('num', r'#.length', receiver);
     return Arrays.indexOf(receiver, element, start, length);
   } else if (receiver is String) {
-    checkNull(element);
     if (start is !int) throw new ArgumentError(start);
     if (element is !String) throw new ArgumentError(element);
     if (start < 0) return -1; // TODO(ahe): Is this correct?
@@ -268,7 +263,6 @@ lastIndexOf$1(receiver, element) {
     var start = JS('num', r'#.length', receiver);
     return Arrays.lastIndexOf(receiver, element, start);
   } else if (receiver is String) {
-    checkNull(element);
     if (element is !String) throw new ArgumentError(element);
     return JS('int', r'#.lastIndexOf(#)', receiver, element);
   }
@@ -279,7 +273,6 @@ lastIndexOf$2(receiver, element, start) {
   if (isJsArray(receiver)) {
     return Arrays.lastIndexOf(receiver, element, start);
   } else if (receiver is String) {
-    checkNull(element);
     if (element is !String) throw new ArgumentError(element);
     if (start != null) {
       if (start is !num) throw new ArgumentError(start);
@@ -302,8 +295,6 @@ removeRange(receiver, start, length) {
   if (length == 0) {
     return;
   }
-  checkNull(start); // TODO(ahe): This is not specified but co19 tests it.
-  checkNull(length); // TODO(ahe): This is not specified but co19 tests it.
   if (start is !int) throw new ArgumentError(start);
   if (length is !int) throw new ArgumentError(length);
   if (length < 0) throw new ArgumentError(length);
@@ -336,10 +327,7 @@ setRange$4(receiver, start, length, from, startFrom) {
 
   checkMutable(receiver, 'indexed set');
   if (length == 0) return;
-  checkNull(start); // TODO(ahe): This is not specified but co19 tests it.
-  checkNull(length); // TODO(ahe): This is not specified but co19 tests it.
   checkNull(from); // TODO(ahe): This is not specified but co19 tests it.
-  checkNull(startFrom); // TODO(ahe): This is not specified but co19 tests it.
   if (start is !int) throw new ArgumentError(start);
   if (length is !int) throw new ArgumentError(length);
   if (startFrom is !int) throw new ArgumentError(startFrom);
@@ -514,7 +502,7 @@ toRadixString(receiver, radix) {
 
 contains$1(receiver, other) {
   if (receiver is String) {
-    return contains$2(receiver, other, 0);
+    return stringContainsUnchecked(receiver, other, 0);
   } else if (isJsArray(receiver)) {
     for (int i = 0; i < receiver.length; i++) {
       if (other == receiver[i]) return true;