Bug 1592140 - enable platform encoder and HW H.264 support on Android. r=jya

Differential Revision: https://phabricator.services.mozilla.com/D51945

--HG--
extra : moz-landing-system : lando

modules/libpref/init/StaticPrefList.yaml

@@ -6351,7 +6351,11 @@
 
 - name: media.webrtc.platformencoder
   type: bool
+#if defined(MOZ_WIDGET_ANDROID)
+  value: true
+#else
   value: false
+#endif
   mirror: always
 
 - name: media.block-autoplay-until-in-foreground
@@ -6365,7 +6369,11 @@
 
 - name: media.webrtc.hw.h264.enabled
   type: bool
+#if defined(MOZ_WIDGET_ANDROID)
+  value: true
+#else
   value: false
+#endif
   mirror: always
 
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