Bug 1081283 - Use the correct calling convention on InitDwriteBG; r=jrmuizel

Otherwise our stack is misaligned by the time we return from this.
This misalignment doesn't cause a crash with the Winodws thread
startup code, but it does with ASAN because it does many things
after the thread entry point exits.

--HG--
extra : rebase_source : 6143788976d8efc9dc5c96030de3b8026d6bbc0f

toolkit/xre/nsAppRunner.cpp

@@ -2853,7 +2853,7 @@ static void LogRegistryEvent(const wchar_t *msg)
 
 #endif
 
-static DWORD InitDwriteBG(LPVOID lpdwThreadParam)
+static DWORD WINAPI InitDwriteBG(LPVOID lpdwThreadParam)
 {
   SetThreadPriority(GetCurrentThread(), THREAD_MODE_BACKGROUND_BEGIN);
   LOGREGISTRY(L"loading dwrite.dll");
@@ -3043,8 +3043,7 @@ XREMain::XRE_mainInit(bool* aExitFlag)
     // FntCache service is ready by the time it's needed.
 
     if (IsVistaOrLater()) {
-      CreateThread(nullptr, 0, (LPTHREAD_START_ROUTINE)&InitDwriteBG,
-                   nullptr, 0, nullptr);
+      CreateThread(nullptr, 0, &InitDwriteBG, nullptr, 0, nullptr);
     }
   }
 #endif