Enable one shot flag by default

By default, enable one-shot optimization.

BUG=v8:8072

Change-Id: I353eb05325b9abfa9b9fab48cf47bad2891798e9
Reviewed-on: https://chromium-review.googlesource.com/1181901Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Commit-Queue: Chandan Reddy <chandanreddy@google.com>
Cr-Commit-Position: refs/heads/master@{#55247}

src/flag-definitions.h

@@ -317,7 +317,7 @@ DEFINE_BOOL(optimize_for_size, false,
             "speed")
 
 // Flag for one shot optimiztions.
-DEFINE_BOOL(enable_one_shot_optimization, false,
+DEFINE_BOOL(enable_one_shot_optimization, true,
             "Enable size optimizations for the code that will "
             "only be executed once")