Fix Regress3540 after r25441.

BUG=
TBR=hpayer@chromium.org

Review URL: https://codereview.chromium.org/746443002

Cr-Commit-Position: refs/heads/master@{#25442}

test/cctest/test-spaces.cc

@@ -222,8 +222,8 @@ TEST(Regress3540) {
   }
   Address address;
   size_t size;
-  address = code_range->AllocateRawMemory(code_range_size - MB,
-                                          code_range_size - MB, &size);
+  address = code_range->AllocateRawMemory(code_range_size - 2 * MB,
+                                          code_range_size - 2 * MB, &size);
   CHECK(address != NULL);
   Address null_address;
   size_t null_size;