Reland^2 "[heap] Enable large objects in young generation"

This is a reland of 932a5ca8

Original change's description:
> [heap] Enable large objects in young generation
>
> Bug: chromium:852420
> Change-Id: Id1cde3450c5ca046029b17eee5dbe5132f299c3d
> Reviewed-on: https://chromium-review.googlesource.com/c/1477212
> Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
> Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#59669}

Bug: chromium:852420
Change-Id: If6dc439e410542da72c3edc08c9926b3edd1186e
Reviewed-on: https://chromium-review.googlesource.com/c/1477736Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59701}

src/flag-definitions.h

@@ -818,7 +818,7 @@ DEFINE_BOOL(fast_promotion_new_space, false,
 
 DEFINE_BOOL(clear_free_memory, false, "initialize free memory with 0")
 
-DEFINE_BOOL(young_generation_large_objects, false,
+DEFINE_BOOL(young_generation_large_objects, true,
             "allocates large objects by default in the young generation large "
             "object space")