ime: Infer key_code when specific key_code is VKEY_UNKNOWN.

[1] broke virtual keyboard PK simulation in some cases, because the VK
was sending VKEY_UNKNOWN as the key_code.

Previously, when key_code is VKEY_UNKNOWN, the key_code was inferred
from the `code`. However, after [1], we only inferred if the key_code
was left out.

[1] https://chromium-review.googlesource.com/c/chromium/src/+/2566868

Bug: 1159250
Change-Id: Ied31078e213fe9bc2f5129057d1e1d34e41e2779
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2592074Reviewed-by: Keith Lee <keithlee@chromium.org>
Commit-Queue: Darren Shen <shend@chromium.org>
Cr-Commit-Position: refs/heads/master@{#837430}

chrome/browser/extensions/api/input_ime/input_ime_api.cc

@@ -109,8 +109,9 @@ ui::KeyEvent ConvertKeyboardEventToUIKeyEvent(
           : ui::ET_KEY_RELEASED;
 
   const auto key_code = static_cast<ui::KeyboardCode>(
-      event.key_code ? *event.key_code
-                     : ui::DomKeycodeToKeyboardCode(event.code));
+      event.key_code && *event.key_code != ui::VKEY_UNKNOWN
+          ? *event.key_code
+          : ui::DomKeycodeToKeyboardCode(event.code));
 
   int flags = ui::EF_NONE;
   flags |= event.alt_key && *event.alt_key ? ui::EF_ALT_DOWN : ui::EF_NONE;