blink: permissions: add plumbing to request permissions

public/platform/modules/permissions/WebPermissionClient.h

Index: public/platform/modules/permissions/WebPermissionClient.h
diff --git a/public/platform/modules/permissions/WebPermissionClient.h b/public/platform/modules/permissions/WebPermissionClient.h
index d0426280dcac876457f522d454fd50f3d81fb9ed..5a1a2e721bfd66f358121c2d90a386f40f1f83be 100644
--- a/public/platform/modules/permissions/WebPermissionClient.h
+++ b/public/platform/modules/permissions/WebPermissionClient.h
@@ -23,6 +23,9 @@ public:
     // Query the permission status of a given origin for a specific permission.
     virtual void queryPermission(WebPermissionType, const WebURL&, WebPermissionCallback*) { }
 
+    // Request a specific permission for a given origin.
+    virtual void requestPermission(WebPermissionType, const WebURL&, WebPermissionCallback*) { }
+
     // Revoke a specific permission for a given origin.
     virtual void revokePermission(WebPermissionType, const WebURL&, WebPermissionCallback*) { }