8035057: NewSize ergonomics wrong when setting small or unaligned size on command line

Summary: Making sure that if NewSize is set on the command line it should be used for both min and initial size even if it is re-aligned.
Reviewed-by: jwilhelm, jmasa

src/share/vm/memory/collectorPolicy.cpp

@@ -307,10 +307,13 @@ void GenCollectorPolicy::initialize_flags() {
   }
 
   // Now take the actual NewSize into account. We will silently increase NewSize
-  // if the user specified a smaller value.
+  // if the user specified a smaller or unaligned value.
   smallest_new_size = MAX2(smallest_new_size, (uintx)align_size_down(NewSize, _gen_alignment));
   if (smallest_new_size != NewSize) {
-    FLAG_SET_ERGO(uintx, NewSize, smallest_new_size);
+    // Do not use FLAG_SET_ERGO to update NewSize here, since this will override
+    // if NewSize was set on the command line or not. This information is needed
+    // later when setting the initial and minimum young generation size.
+    NewSize = smallest_new_size;
   }
   _initial_gen0_size = NewSize;