Replace NULL with nullptr

Also fixed some lines that were too long, and a few other minor
details.

Change-Id: I6efba5fb6e03eb5d0a300fddb2a75bf8e2f175cb
diff --git a/runtime/native/java_lang_Class.cc b/runtime/native/java_lang_Class.cc
index 51a897d..b0d923b 100644
--- a/runtime/native/java_lang_Class.cc
+++ b/runtime/native/java_lang_Class.cc
@@ -42,7 +42,7 @@
     const ScopedFastNativeObjectAccess& soa, jobject java_class)
     SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
   mirror::Class* c = soa.Decode<mirror::Class*>(java_class);
-  DCHECK(c != NULL);
+  DCHECK(c != nullptr);
   DCHECK(c->IsClass());
   // TODO: we could EnsureInitialized here, rather than on every reflective get/set or invoke .
   // For now, we conservatively preserve the old dalvik behavior. A quick "IsInitialized" check