ios: Default preload delay WebState reset workaround to enabled.

Bug: 1139891
Change-Id: I004ba7508671f405ea414c74bc20a65a9ec08be2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2484263
Auto-Submit: Justin Cohen <justincohen@chromium.org>
Reviewed-by: Rohit Rao <rohitrao@chromium.org>
Commit-Queue: Justin Cohen <justincohen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#818508}

ios/chrome/browser/prerender/preload_controller.mm

@@ -146,7 +146,7 @@ static const size_t kMaximumCancelledWebStateDelay = 2;
 
 // Used to enable the workaround for a WebKit crash, see crbug.com/1032928.
 const base::Feature kPreloadDelayWebStateReset{
-    "PreloadDelayWebStateReset", base::FEATURE_DISABLED_BY_DEFAULT};
+    "PreloadDelayWebStateReset", base::FEATURE_ENABLED_BY_DEFAULT};
 
 }  // namespace