Not able to scroll BrowserFrames on iOS Devices (#14813)

Added CSS fixes.

Change-Id: I1f1d27a18b925ab9b4e21292218c75206d3d4984

WebContent/VAADIN/themes/base/browserframe/browserframe.scss

@@ -4,6 +4,13 @@
 	.v-browserframe {
 		font-size: 0;
 	}
+
+	/* fix for #14813 - unable to scroll on iOS devices */
+	.v-webkit.v-ios & .v-browserframe {
+		-webkit-overflow-scrolling: touch;
+		overflow:auto;
+	}
+
 	/* Some times a browser frame can contain a span with altenate text */
 	.v-browserframe > span {
 		font-size: $font-size;

WebContent/VAADIN/themes/valo/shared/_global.scss

@@ -121,6 +121,12 @@ $valo-global-included: false !default;
       -webkit-overflow-scrolling: none;
     }
 
+    //fix for #14813 - unable to scroll on iOS devices
+    .v-webkit.v-ios .v-browserframe {
+      -webkit-overflow-scrolling: touch;
+      overflow:auto;
+    }
+
     .v-assistive-device-only {
       position: absolute;
       top: -2000px;