[PLT-2802] Memory leaks in file upload shortcuts (#2889)

* Added file upload shortcuts (CTRL+U and CMD+U)

* Added KeyCode for U

* Preventing memory leaks

webapp/components/file_upload.jsx

@@ -129,9 +129,7 @@ class FileUpload extends React.Component {
     }
 
     componentDidMount() {
-        var inputDiv = ReactDOM.findDOMNode(this.refs.input);
         var self = this;
-        const {formatMessage} = this.props.intl;
 
         if (this.props.postType === 'post') {
             $('.row.main').dragster({
@@ -177,7 +175,29 @@ class FileUpload extends React.Component {
             });
         }
 
-        document.addEventListener('paste', (e) => {
+        document.addEventListener('paste', this.pasteUpload);
+        document.addEventListener('keydown', this.keyUpload);
+    }
+
+    componentWillUnmount() {
+        let target;
+        if (this.props.postType === 'post') {
+            target = $('.row.main');
+        } else {
+            target = $('.post-right__container');
+        }
+
+        document.removeEventListener('paste', this.pasteUpload);
+        document.removeEventListener('keydown', this.keyUpload);
+
+        // jquery-dragster doesn't provide a function to unregister itself so do it manually
+        target.off('dragenter dragleave dragover drop dragster:enter dragster:leave dragster:over dragster:drop');
+    }
+
+    pasteUpload(e) {
+        var inputDiv = ReactDOM.findDOMNode(this.refs.input);
+        const {formatMessage} = this.props.intl;
+
         if (!e.clipboardData) {
             return;
         }
@@ -222,7 +242,6 @@ class FileUpload extends React.Component {
                     if (Constants.IMAGE_TYPES.indexOf(ext) < 0) {
                         continue;
                     }
-
                     var channelId = self.props.channelId || ChannelStore.getCurrentId();
 
                     // generate a unique id that can be used by other components to refer back to this file upload
@@ -260,26 +279,12 @@ class FileUpload extends React.Component {
                 }
             }
         }
-        });
+    }
 
-        document.addEventListener('keydown', (e) => {
-            //CTRL+U or CMD+U for file uploads
+    keyUpload(e) {
         if ((e.ctrlKey || e.metaKey) && e.keyCode === Constants.KeyCodes.U) {
             $(this.refs.input).focus().trigger('click');
         }
-        });
-    }
-
-    componentWillUnmount() {
-        let target;
-        if (this.props.postType === 'post') {
-            target = $('.row.main');
-        } else {
-            target = $('.post-right__container');
-        }
-
-        // jquery-dragster doesn't provide a function to unregister itself so do it manually
-        target.off('dragenter dragleave dragover drop dragster:enter dragster:leave dragster:over dragster:drop');
     }
 
     cancelUpload(clientId) {