Bug 1619317, ensure we set isWow64 to the correct value after taking it off the main thread r=aklotz

Differential Revision: https://phabricator.services.mozilla.com/D65127

--HG--
extra : moz-landing-system : lando

xpcom/base/nsSystemInfo.cpp

@@ -570,20 +570,20 @@ nsresult CollectProcessInfo(ProcessInfo& info) {
   typedef BOOL(WINAPI * LPFN_IWP2)(HANDLE, USHORT*, USHORT*);
   LPFN_IWP2 iwp2 = reinterpret_cast<LPFN_IWP2>(
       GetProcAddress(GetModuleHandle(L"kernel32"), "IsWow64Process2"));
-  BOOL isWow64 = false;
+  BOOL isWow64 = FALSE;
   USHORT processMachine = IMAGE_FILE_MACHINE_UNKNOWN;
   USHORT nativeMachine = IMAGE_FILE_MACHINE_UNKNOWN;
   BOOL gotWow64Value;
   if (iwp2) {
     gotWow64Value = iwp2(GetCurrentProcess(), &processMachine, &nativeMachine);
     if (gotWow64Value) {
-      info.isWow64 = (processMachine != IMAGE_FILE_MACHINE_UNKNOWN);
+      isWow64 = (processMachine != IMAGE_FILE_MACHINE_UNKNOWN);
     }
   } else {
     gotWow64Value = IsWow64Process(GetCurrentProcess(), &isWow64);
     // The function only indicates a WOW64 environment if it's 32-bit x86
     // running on x86-64, so emulate what IsWow64Process2 would have given.
-    if (gotWow64Value && info.isWow64) {
+    if (gotWow64Value && isWow64) {
       processMachine = IMAGE_FILE_MACHINE_I386;
       nativeMachine = IMAGE_FILE_MACHINE_AMD64;
     }
@@ -591,6 +591,7 @@ nsresult CollectProcessInfo(ProcessInfo& info) {
   NS_WARNING_ASSERTION(gotWow64Value, "IsWow64Process failed");
   if (gotWow64Value) {
     // Set this always, even for the x86-on-arm64 case.
+    info.isWow64 = !!isWow64;
     // Additional information if we're running x86-on-arm64
     info.isWowARM64 = (processMachine == IMAGE_FILE_MACHINE_I386 &&
                        nativeMachine == IMAGE_FILE_MACHINE_ARM64);