[Android] Synthetic composition event should have DomKey 'Unidentified'

content/browser/renderer_host/input/web_input_event_builders_android.cc

Index: content/browser/renderer_host/input/web_input_event_builders_android.cc
diff --git a/content/browser/renderer_host/input/web_input_event_builders_android.cc b/content/browser/renderer_host/input/web_input_event_builders_android.cc
index 6ccde311950b19cc20e0ecc771edcb6ff68ca0f5..c0ffc1b068390dd81b3aa1d67fcbf8c4fc405fef 100644
--- a/content/browser/renderer_host/input/web_input_event_builders_android.cc
+++ b/content/browser/renderer_host/input/web_input_event_builders_android.cc
@@ -45,6 +45,10 @@ ui::DomKey GetDomKeyFromEvent(
     int keycode,
     int modifiers,
     int unicode_character) {
+  // Synthetic key event, not enough information to get DomKey.
+  if (android_key_event.is_null() && !unicode_character)
+    return ui::DomKey::UNIDENTIFIED;

[chongz, 2016/03/17 15:50:39]

Sorry for the confusing logic... Will this look better?
If the event came from |setComposingText()| or it's a synthetic |Char| event
|android_key_event| will be null, otherwise we should have |android_key_event|
if it came from |sendKeyEvent()|.

For 229 if it's AKEYCODE_LAST_CHANNEL it should come from |sendKeyEvent()| and
has |android_key_event|.

However I'm not able to find a hardware with the key (seems to be some kind of
TV remote?) to test, but I've added a pair of unit tests, hope it would be good.

Thanks!

+
   if (!unicode_character && env) {
     // According to spec |kAllowedModifiers| should be Shift and AltGr, however
     // Android doesn't have AltGr key and ImeAdapter::getModifiers won't pass it