[PiP Android API] Enable pip api by default.

Bug: 997324
Change-Id: I250edb4d588b78a5bc7dc29763ee22f68204ee77
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1769228Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Commit-Queue: Jazz Xu <jazzhsu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#690445}

media/base/media_switches.cc

@@ -431,7 +431,7 @@ const base::Feature kDisableSurfaceLayerForVideo{
 
 // Enable picture in picture web api for android.
 const base::Feature kPictureInPictureAPI{"PictureInPictureAPI",
-                                         base::FEATURE_DISABLED_BY_DEFAULT};
+                                         base::FEATURE_ENABLED_BY_DEFAULT};
 
 // Enables CanPlayType() (and other queries) for HLS MIME types. Note that
 // disabling this also causes navigation to .m3u8 files to trigger downloading