Bug 5150869: Text selection enabled in browser.

After text selection is started, rebuildWebTextView is called, which
calls setHorizontallyScrolling with false (multi-line). This was already
its value, but since there was no test for a value change, the layout was
nulled and this stops the selection mode.

Change-Id: I99aadbf45fca4fbdbe8ab7266fe9a7ff839e2792