Issue #2161 - Ctrl + Enter should cause keypress event even though the key combination doesn't input any character

Currently, we dispatch keypress event when Enter is pressed without
modifiers or only with the Shift key (line break).
However, other browsers dispatch keypress events for Ctrl + Enter also
even if it doesn't cause any text input.

So, we should fire keypress events for Ctrl + Enter, even in strict
keypress dispatching mode. Note that with other modifiers, it depends on
the browser and/or platform and we can't dispatch the event for
consistent behavior.

This means web developers shouldn't rely one keypress events to catch
Alt + Enter, Meta + Enter and two or more modifiers + Enter.

Based on BZ 1438133
Resolves #2161

widget/TextEventDispatcher.cpp

@@ -538,8 +538,7 @@ TextEventDispatcher::DispatchKeyboardEventInternal(
 
   if (!sDispatchKeyPressEventNonPrintableInContent &&
       keyEvent.mMessage == eKeyPress &&
-      !keyEvent.IsInputtingText() &&
-      !keyEvent.IsInputtingLineBreak()) {
+      !keyEvent.ShouldKeyPressEventBeFiredOnContent()) {
     keyEvent.mFlags.mOnlySystemGroupDispatchInContent = true;
   }