Preserve scroll view properties by default.

I have sent a heads up to the team about this change.

Change-Id: If1dca2ebd3e5289edb969eb03394a44ca7eb0776
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2094387Reviewed-by: Eugene But <eugenebut@chromium.org>
Commit-Queue: Hiroshi Ichikawa <ichikawa@chromium.org>
Cr-Commit-Position: refs/heads/master@{#749437}

ios/web/common/features.mm

@@ -42,7 +42,7 @@ const base::Feature kUseDefaultUserAgentInWebClient{
     "UseDefaultUserAgentInWebClient", base::FEATURE_DISABLED_BY_DEFAULT};
 
 const base::Feature kPreserveScrollViewProperties{
-    "PreserveScrollViewProperties", base::FEATURE_DISABLED_BY_DEFAULT};
+    "PreserveScrollViewProperties", base::FEATURE_ENABLED_BY_DEFAULT};
 
 }  // namespace features
 }  // namespace web