[win] Don't drop text when IME dialog composition is accepted w/Enter

With #5230, now that we can show the IME dialog on Windows, when we
are selecting a specific word/composition in the IME dialog, if we
press Enter we'll receive that Enter onKeyUp(). It's better if we
process the Enter key onKeyDown() (as the IME enter key is not
received in that case).

src/app/ui/editor/writing_text_state.cpp

@@ -443,12 +443,7 @@ bool WritingTextState::onSetCursor(Editor* editor, const gfx::Point& mouseScreen
   return true;
 }
 
-bool WritingTextState::onKeyDown(Editor*, KeyMessage*)
+bool WritingTextState::onKeyDown(Editor*, KeyMessage* msg)
-{
-  return false;
-}
-
-bool WritingTextState::onKeyUp(Editor*, KeyMessage* msg)
 {
   // Cancel loop pressing Esc key
   if (msg->scancode() == ui::kKeyEsc) {
@@ -457,7 +452,17 @@ bool WritingTextState::onKeyUp(Editor*, KeyMessage* msg)
   // Drop text pressing Enter key
   else if (msg->scancode() == ui::kKeyEnter) {
     drop();
+    return true;
   }
+  return false;
+}
+
+bool WritingTextState::onKeyUp(Editor*, KeyMessage* msg)
+{
+  // Note: We cannot process kKeyEnter key here to drop the text as it
+  // could be received after the Enter key is pressed in the IME
+  // dialog to accept the composition (not to accept the text). So we
+  // process kKeyEnter in onKeyDown().
   return true;
 }