Fix bogus unreachable in debug code.

BUG=none
TEST=none
TBR=jkummerow@chromium.org

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8247 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/hydrogen.cc

@@ -3896,6 +3896,8 @@ HInstruction* HGraphBuilder::BuildStoreKeyedSpecializedArrayElement(
     }
     case JSObject::EXTERNAL_FLOAT_ELEMENTS:
     case JSObject::EXTERNAL_DOUBLE_ELEMENTS:
+      break;
+
     case JSObject::FAST_ELEMENTS:
     case JSObject::FAST_DOUBLE_ELEMENTS:
     case JSObject::DICTIONARY_ELEMENTS: