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/jdwp/jdwp.h b/runtime/jdwp/jdwp.h
index 8dffee6..55441c9 100644
--- a/runtime/jdwp/jdwp.h
+++ b/runtime/jdwp/jdwp.h
@@ -127,7 +127,7 @@
    * Among other things, this binds to a port to listen for a connection from
    * the debugger.
    *
-   * Returns a newly-allocated JdwpState struct on success, or NULL on failure.
+   * Returns a newly-allocated JdwpState struct on success, or nullptr on failure.
    */
   static JdwpState* Create(const JdwpOptions* options)
       LOCKS_EXCLUDED(Locks::mutator_lock_);
diff --git a/runtime/jdwp/jdwp_expand_buf.cc b/runtime/jdwp/jdwp_expand_buf.cc
index cc85cdd..e492d7e 100644
--- a/runtime/jdwp/jdwp_expand_buf.cc
+++ b/runtime/jdwp/jdwp_expand_buf.cc
@@ -156,7 +156,7 @@
 }
 
 /*
- * Add a UTF8 string as a 4-byte length followed by a non-NULL-terminated
+ * Add a UTF8 string as a 4-byte length followed by a non-nullptr-terminated
  * string.
  *
  * Because these strings are coming out of the VM, it's safe to assume that
diff --git a/runtime/jdwp/jdwp_handler.cc b/runtime/jdwp/jdwp_handler.cc
index 2457f14..8e9ab32 100644
--- a/runtime/jdwp/jdwp_handler.cc
+++ b/runtime/jdwp/jdwp_handler.cc
@@ -133,7 +133,7 @@
 
   if (is_constructor) {
     // If we invoked a constructor (which actually returns void), return the receiver,
-    // unless we threw, in which case we return NULL.
+    // unless we threw, in which case we return null.
     resultTag = JT_OBJECT;
     resultValue = (exceptObjId == 0) ? object_id : 0;
   }