Autoplay: use an autoplay policy setting in Blink.

third_party/WebKit/Source/core/frame/Settings.json5

Index: third_party/WebKit/Source/core/frame/Settings.json5
diff --git a/third_party/WebKit/Source/core/frame/Settings.json5 b/third_party/WebKit/Source/core/frame/Settings.json5
index 7cac80b9b7fc1e797a51ad45ec564bee1cc00b09..84b492711ee8d6d63ea75f2bb147504cf877c21c 100644
--- a/third_party/WebKit/Source/core/frame/Settings.json5
+++ b/third_party/WebKit/Source/core/frame/Settings.json5
@@ -215,21 +215,11 @@
       initial: true,
     },
 
-    {
-      name: "mediaPlaybackRequiresUserGesture",
-      initial: false,
-    },
     {
       name: "mediaPlaybackGestureWhitelistScope",
       type: "String",
     },
 
-    // This flags overrides mediaPlaybackRequiresUserGesture
-    {
-      name: "crossOriginMediaPlaybackRequiresUserGesture",
-      initial: false,
-    },
-
     {
       name: "presentationRequiresUserGesture",
       initial: true,
@@ -927,5 +917,12 @@
       name: "doNotUpdateSelectionOnMutatingSelectionRange",
       initial: false,
     },
+
+    // Defines the autoplay policy to use.
+    {
+      name: "autoplayPolicy",
+      type: "AutoplayPolicy::Type",
+      initial: "AutoplayPolicy::Type::kNoUserGestureRequired",
+    },
   ],
 }