Enable overlays for fullscreen-div cases on Android.

Bug: 618368
Change-Id: Ida7033ce771a2a7b29e0a49eb425ff67ace4791f
Reviewed-on: https://chromium-review.googlesource.com/677408Reviewed-by: Thomas Guilbert <tguilbert@chromium.org>
Commit-Queue: Frank Liberato <liberato@chromium.org>
Cr-Commit-Position: refs/heads/master@{#503551}

media/base/media_switches.cc

@@ -213,7 +213,7 @@ const base::Feature kUseAndroidOverlay{"UseAndroidOverlay",
 // Use AndroidOverlay for more cases than just player-element fullscreen?  This
 // requires that |kUseAndroidOverlay| is true, else it is ignored.
 const base::Feature kUseAndroidOverlayAggressively{
-    "UseAndroidOverlayAggressively", base::FEATURE_DISABLED_BY_DEFAULT};
+    "UseAndroidOverlayAggressively", base::FEATURE_ENABLED_BY_DEFAULT};
 
 // Let video track be unselected when video is playing in the background.
 const base::Feature kBackgroundVideoTrackOptimization{