Revert "[turbofan] Temporarily turn off escape analysis."

This reverts commit 2b15425b.

Reason for revert: Re-enabling escape analysis after merging the flag change to 6.1.

Original change's description:
> [turbofan] Temporarily turn off escape analysis.
> 
> Bug: chromium:765433
> Change-Id: Iecc9540f6305bc24a0a5210c149b55403b9ce09d
> Reviewed-on: https://chromium-review.googlesource.com/667106
> Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
> Commit-Queue: Jaroslav Sevcik <jarin@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#48032}

TBR=mstarzinger@chromium.org,jarin@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: chromium:765433
Change-Id: Icac44fd76e2965df1e143700941b628ea7a69166
Reviewed-on: https://chromium-review.googlesource.com/670864Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Jaroslav Sevcik <jarin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48064}

src/flag-definitions.h

@@ -445,7 +445,7 @@ DEFINE_BOOL(turbo_loop_peeling, true, "Turbofan loop peeling")
 DEFINE_BOOL(turbo_loop_variable, true, "Turbofan loop variable optimization")
 DEFINE_BOOL(turbo_cf_optimization, true, "optimize control flow in TurboFan")
 DEFINE_BOOL(turbo_frame_elision, true, "elide frames in TurboFan")
-DEFINE_BOOL(turbo_escape, false, "enable escape analysis")
+DEFINE_BOOL(turbo_escape, true, "enable escape analysis")
 DEFINE_BOOL(turbo_instruction_scheduling, false,
             "enable instruction scheduling in TurboFan")
 DEFINE_BOOL(turbo_stress_instruction_scheduling, false,