Bug 1732208 - Silence the unused-but-set-variable warning in widget. r=cmartin

widget/windows/nsAppShell.cpp(685,10): error: variable 'uiMessage' set but not used [-Werror,-Wunused-but-set-variable]
    bool uiMessage = false;
         ^
widget/windows/TaskbarPreview.cpp(370,11): error: variable 'hr' set but not used [-Werror,-Wunused-but-set-variable]
  HRESULT hr;
          ^

Differential Revision: https://phabricator.services.mozilla.com/D126461

widget/windows/TaskbarPreview.cpp

@@ -375,6 +375,7 @@ TaskbarPreviewCallback::Done(nsISupports* aCanvas, bool aDrawBorder) {
     hr = DwmSetIconicThumbnail(mPreview->PreviewWindow(), hBitmap, flags);
   }
   MOZ_ASSERT(SUCCEEDED(hr));
+  (void)hr;
   return NS_OK;
 }
 

widget/windows/nsAppShell.cpp

@@ -682,7 +682,6 @@ bool nsAppShell::ProcessNextNativeEvent(bool mayWait) {
 
   do {
     MSG msg;
-    bool uiMessage = false;
 
     // For avoiding deadlock between our process and plugin process by
     // mouse wheel messages, we're handling actually when we receive one of
@@ -696,15 +695,10 @@ bool nsAppShell::ProcessNextNativeEvent(bool mayWait) {
                                          MOZ_WM_MOUSEWHEEL_LAST, PM_REMOVE);
       NS_ASSERTION(gotMessage,
                    "waiting internal wheel message, but it has not come");
-      uiMessage = gotMessage;
     }
 
     if (!gotMessage) {
       gotMessage = WinUtils::PeekMessage(&msg, nullptr, 0, 0, PM_REMOVE);
-      uiMessage =
-          (msg.message >= WM_KEYFIRST && msg.message <= WM_IME_KEYLAST) ||
-          (msg.message >= NS_WM_IMEFIRST && msg.message <= NS_WM_IMELAST) ||
-          (msg.message >= WM_MOUSEFIRST && msg.message <= WM_MOUSELAST);
     }
 
     if (gotMessage) {