internal-links: Download file attachment links using downloadURL.

This commit download file attachments using downloadURL method of
webContent, the same way loadURL opens internal links. This
removes the use of hidden webview added in
f70432f.

Improves: #469.

Author: abhigyank

app/renderer/css/main.css

@@ -284,11 +284,6 @@ webview {
     flex-direction: column;
 }
 
-webview.download-webview {
-  z-index: -1;
-  pointer-events: none;
-}
-
 webview.onload {
     transition: opacity 1s cubic-bezier(0.95, 0.05, 0.795, 0.035);
 }

app/renderer/js/components/handle-external-link.js

@@ -1,7 +1,6 @@
 const { shell } = require('electron').remote;
 const LinkUtil = require('../utils/link-util');
 const DomainUtil = require('../utils/domain-util');
-const hiddenWebView = require('../components/hidden-webview');
 
 function handleExternalLink(event) {
 	const { url } = event;
@@ -16,12 +15,12 @@ function handleExternalLink(event) {
 	if (isWhiteListURL) {
 		event.preventDefault();
 
-    // only open the  pdf, mp3, mp4 etc.. in hidden webview since opening the
-    // image in webview will do nothing and will not save it
-    // whereas the pdf will be saved to user desktop once openened in
-    // in the hidden webview and will not trigger webview reload
+    // download txt, pdf, mp3, mp4 etc.. by using downloadURL in the
+    // main process which allows the user to save the files to their desktop
+    // and not trigger webview reload while image in webview will
+    // do nothing and will not save it
 		if (!LinkUtil.isImage(url) && isUploadsURL) {
-			hiddenWebView.loadURL(url);
+			this.$el.downloadURL(url);
 			return;
 		}