<webview>: First stab at implementing media permission request for guests.

chrome/renderer/resources/extensions/web_view.js

Index: chrome/renderer/resources/extensions/web_view.js
diff --git a/chrome/renderer/resources/extensions/web_view.js b/chrome/renderer/resources/extensions/web_view.js
index c923edce7fadd8668c2767fa426bfe419f1cf289..47fa0bf12d08180fd68c4fa943ae343fe555f3fe 100644
--- a/chrome/renderer/resources/extensions/web_view.js
+++ b/chrome/renderer/resources/extensions/web_view.js
@@ -114,6 +114,7 @@ function WebView(node) {
   for (var eventName in WEB_VIEW_EVENTS) {
     this.setupEvent_(eventName, WEB_VIEW_EVENTS[eventName]);
   }
+  this.maybeSetupPermissionEvent_();
 }
 
 /**
@@ -135,7 +136,7 @@ WebView.prototype.handleObjectMutation_ = function(mutation) {
 /**
  * @private
  */
-WebView.prototype.setupEvent_ = function(eventname, attribs) {
+WebView.prototype.setupEvent_ = function(eventname, attribs, opt_prepareEvent) {
   var node = this.node_;
   this.objectNode_.addEventListener('-internal-' + eventname, function(e) {
     var evt = new Event(eventname);
@@ -143,6 +144,17 @@ WebView.prototype.setupEvent_ = function(eventname, attribs) {
     attribs.forEach(function(attribName) {
       evt[attribName] = detail[attribName];
     });
+    if (opt_prepareEvent) {
+      opt_prepareEvent(evt, detail);
+    }
     node.dispatchEvent(evt);
   });
-}
+};
+
+/**
+ * Implemented when webview.permissionAPI permission is available.
+ * @private
+ */
+WebView.prototype.maybeSetupPermissionEvent_ = function() {};
+
+exports.WebView = WebView;