macviews: Flip ViewsBrowserMode default

Change-Id: Ife1da1c63b1c2cd2b373c2aa6e349e82e1c6ee7b
Reviewed-on: https://chromium-review.googlesource.com/977949Reviewed-by: Avi Drissman <avi@chromium.org>
Commit-Queue: Elly Fong-Jones <ellyjones@chromium.org>
Cr-Commit-Position: refs/heads/master@{#578334}

ui/base/ui_base_features.cc

@@ -152,7 +152,7 @@ bool HostWindowsInAppShimProcess() {
 // Causes Views browser builds to use Views browser windows by default rather
 // than Cocoa browser windows.
 const base::Feature kViewsBrowserWindows{"ViewsBrowserWindows",
-                                         base::FEATURE_DISABLED_BY_DEFAULT};
+                                         base::FEATURE_ENABLED_BY_DEFAULT};
 
 // Returns whether a Views-capable browser build should use the Cocoa browser
 // UI.