Bug 327413

When an input method commits text without a preedit, for example a keyboard that commits a whole suggestion at once, the page receives compositionend, and a beforeinput with inputType insertFromComposition, but no compositionstart. InputMethodFilter::committed() calls webkitWebViewConfirmComposition(), which ends in Editor::setComposition(text, ConfirmComposition). That always dispatches compositionend, whether or not a composition was in progress. Steps (API test): focus a textarea, then emit "committed" with "hello" on the input method context, with no preedit before it. The text is inserted, and the page gets one compositionend and no compositionstart. Expected: either no composition events, with the text inserted as typing (inputType insertText), or a compositionstart before the compositionend. Pages that track composition state, such as rich text editors, can be confused by an unpaired compositionend. Seen first with wpe-android, whose keyboard integration commits every suggestion this way. Bug 84394 reported the same symptom in 2012 for number keys typed through an input method. Today's key handling path skips one-character commits, but commits outside key handling still get an unpaired compositionend.