Fix GN build after r23442.

R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/514583003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23448 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

BUILD.gn

@@ -462,6 +462,8 @@ source_set("v8_base") {
     "src/compilation-cache.h",
     "src/compiler/ast-graph-builder.cc",
     "src/compiler/ast-graph-builder.h",
+    "src/compiler/change-lowering.cc",
+    "src/compiler/change-lowering.h",
     "src/compiler/code-generator-impl.h",
     "src/compiler/code-generator.cc",
     "src/compiler/code-generator.h",