Simplify ConfigureHeap and change --max_new_space_size to --max_semi_space_size.

src/flag-definitions.h

Index: src/flag-definitions.h
diff --git a/src/flag-definitions.h b/src/flag-definitions.h
index 30cbcd7bc60fbf6f2f08153fc46b093fb903b7a9..87d4242dd6fc5b80ce655cc7c5cef55b204dfa64 100644
--- a/src/flag-definitions.h
+++ b/src/flag-definitions.h
@@ -463,9 +463,9 @@ DEFINE_bool(always_inline_smi_code, false,
             "always inline smi code in non-opt code")
 
 // heap.cc
-DEFINE_int(max_new_space_size, 0,
-    "max size of the new space consisting of two semi-spaces which are half"
-    "the size (in MBytes)")
+DEFINE_int(max_semi_space_size, 0,
+    "max size of a semi-space (in MBytes), the new space consists of two"
+    "semi-spaces")
 DEFINE_int(max_old_space_size, 0, "max size of the old space (in Mbytes)")
 DEFINE_int(max_executable_size, 0, "max size of executable memory (in Mbytes)")
 DEFINE_bool(gc_global, false, "always perform global GCs")