Change compose box inputs from controlled to 'not controlled'

Fixes zulip#2589

* make sure we do update input's initial values using `updateTextInput`
in `componentDidMount`
* remove the `value={...}` props that make the inputs controlled

src/compose/ComposeBox.js

@@ -247,6 +247,13 @@ class ComposeBox extends PureComponent<Props, State> {
     }
   };
 
+  componentDidMount() {
+    const { message, topic } = this.state;
+
+    updateTextInput(this.messageInput, message);
+    updateTextInput(this.topicInput, topic);
+  }
+
   componentWillUnmount() {
     this.tryUpdateDraft();
   }
@@ -328,7 +335,6 @@ class ComposeBox extends PureComponent<Props, State> {
                 onFocus={this.handleTopicFocus}
                 onBlur={this.handleTopicBlur}
                 onTouchStart={this.handleInputTouchStart}
-                value={topic}
               />
             )}
             <MultilineInput
@@ -340,7 +346,6 @@ class ComposeBox extends PureComponent<Props, State> {
                   messageInputRef(component);
                 }
               }}
-              value={message}
               onBlur={this.handleMessageBlur}
               onChange={this.handleMessageChange}
               onFocus={this.handleMessageFocus}