Plugins: Fix plugin modal scrollbar visibility.

Set height of scrollable container to exclude the modal footer so that the bottom of the scrollbar remains visible and accessible. Simplify styling by eliminating small viewport height adjustment. Change modal positioning in mobile viewports to ensure entire modal is visible with a masked margin.

Developed in WordPress#11957

Props projektisle, alanjacobmathew, joedolson, sabernhardt.
Fixes #65334.

git-svn-id: https://develop.svn.wordpress.org/trunk@62691 602fd350-edb4-49c9-b593-d223f7449a82

Author: joedolson

src/js/_enqueues/admin/plugin-install.js

@@ -20,7 +20,7 @@ jQuery( function( $ ) {
 
 	window.tb_position = function() {
 		var width = $( window ).width(),
-			H = $( window ).height() - ( ( 792 < width ) ? 60 : 20 ),
+			H = $( window ).height() - ( ( 792 < width ) ? 60 : 40 ),
 			W = ( 792 < width ) ? 772 : width - 20;
 
 		tbWindow = $( '#TB_window' );

src/wp-admin/css/common.css

@@ -2804,7 +2804,7 @@ div.action-links {
 #plugin-information-scrollable {
 	overflow: auto;
 	-webkit-overflow-scrolling: touch;
-	height: 100%;
+	height: calc(100% - 67px);
 }
 
 #plugin-information-title {
@@ -3204,11 +3204,6 @@ div.action-links {
 	#plugin-information .fyi small {
 		display: none;
 	}
-
-	#plugin-information-footer {
-		padding: 12px 16px 0;
-		height: 46px;
-	}
 }
 
 /* Thickbox for the Plugin details modal. */