[heap] Use smaller minimum allocation limit growing step when optimizing for memory usage.

test/mjsunit/regress/regress-crbug-500497.js

Index: test/mjsunit/regress/regress-crbug-500497.js
diff --git a/test/mjsunit/regress/regress-crbug-500497.js b/test/mjsunit/regress/regress-crbug-500497.js
index 9117440c2c843fe0b37ee68f5cd059e2b7314d1c..356e4e6942bab34ab539b9e3ba66a950e4a1ff82 100644
--- a/test/mjsunit/regress/regress-crbug-500497.js
+++ b/test/mjsunit/regress/regress-crbug-500497.js
@@ -4,6 +4,7 @@
 
 // New space must be at max capacity to trigger pretenuring decision.
 // Flags: --allow-natives-syntax --verify-heap --max-semi-space-size=1
+// Flags: --expose-gc
 
 var global = [];  // Used to keep some objects alive.
 
@@ -12,6 +13,8 @@ function Ctor() {
   return result;
 }
 
+gc();
+
 for (var i = 0; i < 120; i++) {
   // Make the "a" property long-lived, while everything else is short-lived.
   global.push(Ctor().a);