WhisperSystems/TextSecure — pull request #1118 by tkohlmeier (2014-03-10 22:11:11+00:00)
Title: Display "send" button on the soft keyboard if "enter sends" is activated in the preferences

When "enter sends" is enabled in the preferences, it would be nice to show this to the user by replacing the enter button by a send button.
However, this doesn't work for multiline EditTexts. Fortunately, multiline is not really needed, as the same behavior can be achieved by disabling horizontal scrolling and setting the maximum number of lines (again).
Sell also (answer by HYS): http://stackoverflow.com/questions/2986387/multi-line-edittext-with-done-action-button