Focus the search box on Ctrl/Cmd+F shortcut

For #229

src/browser/index.jsx

@@ -75,6 +75,12 @@ var MainPage = React.createClass({
       this.refs[`mattermostView${this.state.key}`].clearCacheAndReload();
     });
 
+    // activate search box in current tab
+    ipcRenderer.on('activate-search-box', (event) => {
+      let webview = document.getElementById('mattermostView' + thisObj.state.key);
+      webview.send('activate-search-box');
+    });
+
     var focusListener = function() {
       var webview = document.getElementById('mattermostView' + thisObj.state.key);
       webview.focus();

src/browser/webview/mattermost.js

@@ -127,3 +127,16 @@ notification.override({
     ipc.sendToHost('onNotificationClick');
   }
 });
+
+// get the last of href for the current channel in the sidebar.
+function getCurrentChannelString() {
+  const active_channel_link = document.querySelector('.active a.sidebar-channel');
+  const url_elements = active_channel_link.href.split('/');
+  return url_elements[url_elements.length - 1];
+}
+
+ipc.on('activate-search-box', (event) => {
+  const search_box = document.getElementsByClassName('search-bar')[0]; // should use id
+  search_box.focus();
+  console.log(getCurrentChannelString());
+});