Fix syntax error, feel sheepish.

Review URL: http://codereview.chromium.org/6525052

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@6822 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/hydrogen.cc

@@ -3767,7 +3767,7 @@ HInstruction* HGraphBuilder::BuildStoreKeyedPixelArrayElement(
     HValue* object,
     HValue* key,
     HValue* val,
-    XExpression* expr) {
+    Expression* expr) {
   ASSERT(expr->IsMonomorphic());
   AddInstruction(new HCheckNonSmi(object));
   Handle<Map> map = expr->GetMonomorphicReceiverType();