Bug 1571516 - [1/2] preparatory reorganization r=gsvelto

Pull the failing section of code out into its own function, for the sake
of clarity of later diffs.

No functional changes.

Differential Revision: https://phabricator.services.mozilla.com/D186987

widget/windows/nsAppShell.cpp

@@ -361,22 +361,7 @@ nsAppShell::Observe(nsISupports* aSubject, const char* aTopic,
   return nsBaseAppShell::Observe(aSubject, aTopic, aData);
 }
 
-nsresult nsAppShell::Init() {
-  LSPAnnotate();
-
-  hal::Init();
-
-  if (XRE_IsParentProcess()) {
-    sTaskbarButtonCreatedMsg = ::RegisterWindowMessageW(kTaskbarButtonEventId);
-    NS_ASSERTION(sTaskbarButtonCreatedMsg,
-                 "Could not register taskbar button creation message");
-  }
-
-  // The hidden message window is used for interrupting the processing of native
-  // events, so that we can process gecko events. Therefore, we only need it if
-  // we are processing native events. Disabling this is required for win32k
-  // syscall lockdown.
-  if (XRE_UseNativeEventProcessing()) {
+nsresult nsAppShell::InitHiddenWindow() {
   sAppShellGeckoMsgId = ::RegisterWindowMessageW(kAppShellGeckoEventId);
   NS_ASSERTION(sAppShellGeckoMsgId,
                "Could not register hidden window event message!");
@@ -406,6 +391,29 @@ nsresult nsAppShell::Init() {
                             10, 10, HWND_MESSAGE, nullptr, module, nullptr);
   MOZ_DIAGNOSTIC_ASSERT(mEventWnd, "CreateWindowW for EventWindow failed");
   NS_ENSURE_STATE(mEventWnd);
+
+  return NS_OK;
+}
+
+nsresult nsAppShell::Init() {
+  LSPAnnotate();
+
+  hal::Init();
+
+  if (XRE_IsParentProcess()) {
+    sTaskbarButtonCreatedMsg = ::RegisterWindowMessageW(kTaskbarButtonEventId);
+    NS_ASSERTION(sTaskbarButtonCreatedMsg,
+                 "Could not register taskbar button creation message");
+  }
+
+  // The hidden message window is used for interrupting the processing of native
+  // events, so that we can process gecko events. Therefore, we only need it if
+  // we are processing native events. Disabling this is required for win32k
+  // syscall lockdown.
+  if (XRE_UseNativeEventProcessing()) {
+    if (nsresult rv = this->InitHiddenWindow(); NS_FAILED(rv)) {
+      return rv;
+    }
   } else if (XRE_IsContentProcess() && !IsWin32kLockedDown()) {
     // We're not generally processing native events, but still using GDI and we
     // still have some internal windows, e.g. from calling CoInitializeEx.

widget/windows/nsAppShell.h

@@ -19,7 +19,7 @@
 /**
  * Native Win32 Application shell wrapper
  */
-class nsAppShell : public nsBaseAppShell {
+class nsAppShell final : public nsBaseAppShell {
  public:
   nsAppShell()
       : mEventWnd(nullptr),
@@ -49,6 +49,7 @@ class nsAppShell : public nsBaseAppShell {
   static LRESULT CALLBACK EventWindowProc(HWND, UINT, WPARAM, LPARAM);
 
  protected:
+  nsresult InitHiddenWindow();
   HWND mEventWnd;
   bool mNativeCallbackPending;