Bug 1707954: Part 4 - Build fixes to reflect EnsureMTA changes; r=Jamie

Now that we always have an MTA active, we don't need to explicitly try to
start it anymore. These locations in our source were doing so, which is now
not only redundant, but fails (since `EnsureMTA`'s default constructor is now
`private`).

We also fix a spot in `JumpListBuilder` where we need a lambda to capture by
reference to fix a static analysis issue.

Differential Revision: https://phabricator.services.mozilla.com/D113563

dom/media/webrtc/CubebDeviceEnumerator.cpp

@@ -55,7 +55,6 @@ CubebDeviceEnumerator::CubebDeviceEnumerator()
   // Ensure the MTA thread exists and gets instantiated before the
   // CubebDeviceEnumerator so that this instance will always gets destructed
   // before the MTA thread gets shutdown.
-  mozilla::mscom::EnsureMTA();
   mozilla::mscom::EnsureMTA([&]() -> void {
 #endif
     int rv = cubeb_register_device_collection_changed(

js/xpconnect/src/XPCShellImpl.cpp

@@ -53,6 +53,7 @@
 #endif
 
 #ifdef XP_WIN
+#  include "mozilla/mscom/ProcessRuntime.h"
 #  include "mozilla/ScopeExit.h"
 #  include "mozilla/widget/AudioSession.h"
 #  include "mozilla/WinDllServices.h"
@@ -1099,6 +1100,14 @@ int XRE_XPCShellMain(int argc, char** argv, char** envp,
         "*** You are running in chaos test mode. See ChaosMode.h. ***\n");
   }
 
+#ifdef XP_WIN
+  // Some COM settings are global to the process and must be set before any non-
+  // trivial COM is run in the application. Since these settings may affect
+  // stability, we should instantiate COM ASAP so that we can ensure that these
+  // global settings are configured before anything can interfere.
+  mscom::ProcessRuntime mscom;
+#endif
+
   // The provider needs to outlive the call to shutting down XPCOM.
   XPCShellDirProvider dirprovider;
 

widget/windows/JumpListBuilder.cpp

@@ -98,7 +98,7 @@ JumpListBuilder::JumpListBuilder()
   // Instantiate mJumpListMgr in the multithreaded apartment so that proxied
   // calls on that object do not need to interact with the main thread's message
   // pump.
-  mscom::EnsureMTA([this]() {
+  mscom::EnsureMTA([&]() {
     RefPtr<ICustomDestinationList> jumpListMgr;
     HRESULT hr = ::CoCreateInstance(
         CLSID_DestinationList, nullptr, CLSCTX_INPROC_SERVER,

widget/windows/nsFilePicker.cpp

@@ -11,7 +11,6 @@
 #include <cderr.h>
 
 #include "mozilla/BackgroundHangMonitor.h"
-#include "mozilla/mscom/EnsureMTA.h"
 #include "mozilla/ProfilerLabels.h"
 #include "mozilla/UniquePtr.h"
 #include "mozilla/WindowsVersion.h"
@@ -28,7 +27,6 @@
 using mozilla::IsWin8OrLater;
 using mozilla::MakeUnique;
 using mozilla::UniquePtr;
-using mozilla::mscom::EnsureMTA;
 
 using namespace mozilla::widget;
 
@@ -110,15 +108,6 @@ NS_IMETHODIMP nsFilePicker::Init(mozIDOMWindowProxy* aParent,
  * @return true if a file was selected successfully.
  */
 bool nsFilePicker::ShowFolderPicker(const nsString& aInitialDir) {
-  if (!IsWin8OrLater()) {
-    // Some Windows 7 users are experiencing a race condition when some dlls
-    // that are loaded by the file picker cause a crash while attempting to shut
-    // down the COM multithreaded apartment. By instantiating EnsureMTA, we hold
-    // an additional reference to the MTA that should prevent this race, since
-    // the MTA will remain alive until shutdown.
-    EnsureMTA ensureMTA;
-  }
-
   RefPtr<IFileOpenDialog> dialog;
   if (FAILED(CoCreateInstance(CLSID_FileOpenDialog, nullptr,
                               CLSCTX_INPROC_SERVER, IID_IFileOpenDialog,
@@ -206,15 +195,6 @@ bool nsFilePicker::ShowFolderPicker(const nsString& aInitialDir) {
 bool nsFilePicker::ShowFilePicker(const nsString& aInitialDir) {
   AUTO_PROFILER_LABEL("nsFilePicker::ShowFilePicker", OTHER);
 
-  if (!IsWin8OrLater()) {
-    // Some Windows 7 users are experiencing a race condition when some dlls
-    // that are loaded by the file picker cause a crash while attempting to shut
-    // down the COM multithreaded apartment. By instantiating EnsureMTA, we hold
-    // an additional reference to the MTA that should prevent this race, since
-    // the MTA will remain alive until shutdown.
-    EnsureMTA ensureMTA;
-  }
-
   RefPtr<IFileDialog> dialog;
   if (mMode != modeSave) {
     if (FAILED(CoCreateInstance(CLSID_FileOpenDialog, nullptr,