Basically working upload progress bar.

skins/base/css/organisms/RoomView.css

@@ -117,3 +117,14 @@ limitations under the License.
     flex: 0 0 63px;
     margin-right: 2px;
 }
+
+.mx_RoomView_uploadProgressOuter {
+    width: 100%;
+    background-color: black;
+    height: 5px;
+}
+
+.mx_RoomView_uploadProgressInner {
+    background-color: blue;
+    height: 5px;
+}

skins/base/views/molecules/MessageComposer.js

@@ -32,14 +32,8 @@ module.exports = React.createClass({
 
     onUploadFileSelected: function(ev) {
         var files = ev.target.files;
-
+        // MessageComposer shouldn't have to rely on it's parent passing in a callback to upload a file
-        ContentMessages.sendContentToRoom(
+        this.props.uploadFile(files[0]);
-            files[0], this.props.room.roomId, MatrixClientPeg.get()
-        ).progress(function(ev) {
-            //console.log("Upload: "+ev.loaded+" / "+ev.total);
-        }).done(undefined, function() {
-            // display error message
-        });
     },
 
     render: function() {

skins/base/views/organisms/RoomView.js

@@ -22,6 +22,7 @@ var MatrixClientPeg = require("../../../../src/MatrixClientPeg");
 
 var ComponentBroker = require('../../../../src/ComponentBroker');
 var classNames = require("classnames");
+var filesize = require('filesize');
 
 var MessageTile = ComponentBroker.get('molecules/MessageTile');
 var RoomHeader = ComponentBroker.get('molecules/RoomHeader');
@@ -76,6 +77,22 @@ module.exports = React.createClass({
                 <div />
             );
 
+            if (this.state.upload) {
+                var innerProgressStyle = {
+                    width: ((this.state.upload.uploadedBytes / this.state.upload.totalBytes) * 100) + '%'
+                };
+                statusBar = (
+                    <div className="mx_RoomView_uploadBar">
+                        <span className="mx_RoomView_uploadFilename">Uploading {this.state.upload.fileName}</span>
+                        <span className="mx_RoomView_uploadBytes">
+                        {filesize(this.state.upload.uploadedBytes)} / {filesize(this.state.upload.totalBytes)}
+                        </span>
+                        <div className="mx_RoomView_uploadProgressOuter">
+                            <div className="mx_RoomView_uploadProgressInner" style={innerProgressStyle}></div>
+                        </div>
+                    </div>
+                );
+            } else {
                 var typingString = this.getWhoIsTypingString();
                 if (typingString) {
                     statusBar = (
@@ -84,6 +101,7 @@ module.exports = React.createClass({
                         </div>
                     );
                 }
+            }
 
             return (
                 <div className="mx_RoomView">
@@ -105,7 +123,7 @@ module.exports = React.createClass({
                             {statusBar}
                         </div>
                     </div>
-                    <MessageComposer room={this.state.room} />
+                    <MessageComposer room={this.state.room} uploadFile={this.uploadFile} />
                 </div>
             );
         }

src/controllers/organisms/RoomView.js

@@ -231,16 +231,38 @@ module.exports = {
         ev.stopPropagation();
         ev.preventDefault();
         var files = ev.dataTransfer.files;
-
         if (files.length == 1) {
+            this.uploadFile(files[0]);
+        }
+    },
+
+    uploadFile: function(file) {
+        this.setState({
+            upload: {
+                fileName: file.name,
+                uploadedBytes: 0,
+                totalBytes: file.size
+            }
+        });
+        var self = this;
         ContentMessages.sendContentToRoom(
-                files[0], this.props.roomId, MatrixClientPeg.get()
+            file, this.props.roomId, MatrixClientPeg.get()
         ).progress(function(ev) {
             //console.log("Upload: "+ev.loaded+" / "+ev.total);
+            self.setState({
+                upload: {
+                    fileName: file.name,
+                    uploadedBytes: ev.loaded,
+                    totalBytes: ev.total
+                }
+            });
+        }).finally(function() {
+            self.setState({
+                upload: undefined
+            });
         }).done(undefined, function() {
             // display error message
         });
-        }
     },
 
     getWhoIsTypingString: function() {