Bug 1528943 - Stop trying to retrieve raw keycode value when native v…

…irtual keycode is VK_PROCESS r=m_kato

We didn't dispatch keyboard events during composition.  Therefore, we tried to
retrieve raw virtual keycode value when key messages come with `VK_PROCESS`
unexpectedly.  However, the API, `ImmGetVirtualKey()`, is not usable for this
purpose because it always returns `VK_PROCESS` if the key messages have already
been handled by IME.  So, we can just stop using it since we need to expose
such key messages as KeyboardEvent whose `key` value is `Process` and `keyCode`
value is `DOM_VK_PROCESS`.

Differential Revision: https://phabricator.services.mozilla.com/D20623

UltraBlame original commit: a50238785f3d0db6c47a0d8b846f0d3798d6daf5

widget/windows/KeyboardLayout.cpp

@@ -1432,14 +1432,11 @@ void NativeKey::InitWithKeyOrChar() {
 
 
       sLastKeyMSG = mMsg;
+
 
 
-      if (mMsg.wParam == VK_PROCESSKEY) {
-        mOriginalVirtualKeyCode =
-            static_cast<uint8_t>(::ImmGetVirtualKey(mMsg.hwnd));
-      } else {
-        mOriginalVirtualKeyCode = static_cast<uint8_t>(mMsg.wParam);
-      }
+
+      mOriginalVirtualKeyCode = static_cast<uint8_t>(mMsg.wParam);