Reduce allowance in the first code page at start up.

This has become possible since we moved a few experimental
Javascript features to default.

R=hpayer@chromium.org
BUG=chromium:506044
LOG=N

Review URL: https://codereview.chromium.org/1262833002

Cr-Commit-Position: refs/heads/master@{#29916}

src/snapshot/snapshot-common.cc

@@ -137,7 +137,7 @@ void CalculateFirstPageSizes(bool is_default_snapshot,
                   2 * context_reservations[context_index].chunk_size()) +
                  Page::kObjectStartOffset;
       // Add a small allowance to the code space for small scripts.
-      if (space == CODE_SPACE) required += 64 * KB;
+      if (space == CODE_SPACE) required += 32 * KB;
     } else {
       // We expect the vanilla snapshot to only require on page per space.
       DCHECK(!is_default_snapshot);