Bug 1785162 - Allow child-process half-stalls to ride the trains r=glandium,gsvelto

The past couple of weeks of crash telemetry indicate that stalling on
OOM in child processes for half as long as in main processes drastically
reduces child process OOM crashes without noticeably increasing
main-process OOM crashes.

Give it a ticket and send it on its way.

Differential Revision: https://phabricator.services.mozilla.com/D158790

memory/build/mozjemalloc.cpp

@@ -1373,8 +1373,7 @@ static inline void ApplyZeroOrJunk(void* aPtr, size_t aSize) {
   }
 }
 
-// On Windows, delay crashing on OOM. Partly experimental. (See bug 1785145 for
-// more details.)
+// On Windows, delay crashing on OOM.
 #ifdef XP_WIN
 
 // Implementation of VirtualAlloc wrapper (bug 1716727).
@@ -1393,19 +1392,14 @@ struct StallSpecs {
 
 static constexpr StallSpecs maxStall = {.maxAttempts = kMaxAttempts,
                                         .delayMs = kDelayMs};
-static constexpr StallSpecs doNotStall
-    [[maybe_unused]] = {.maxAttempts = 0, .delayMs = 0};
 
-Atomic<bool> sHasStalled{false};
 static inline StallSpecs GetStallSpecs() {
 #  if defined(JS_STANDALONE)
   // GetGeckoProcessType() isn't available in this configuration. (SpiderMonkey
   // on Windows mostly skips this in favor of directly calling ::VirtualAlloc(),
   // though, so it's probably not going to matter whether we stall here or not.)
   return maxStall;
-#  elif defined(NIGHTLY_BUILD)
-  // On Nightly, partly for experiment's sake (bug 1785162):
-  //
+#  else
   switch (GetGeckoProcessType()) {
     // For the main process, stall for the maximum permissible time period. (The
     // main process is the most important one to keep alive.)
@@ -1416,13 +1410,6 @@ static inline StallSpecs GetStallSpecs() {
     default:
       return {.maxAttempts = kMaxAttempts / 2, .delayMs = kDelayMs};
   }
-#  else
-  // In the main process, always stall.
-  if (GetGeckoProcessType() == GeckoProcessType::GeckoProcessType_Default) {
-    return maxStall;
-  }
-  // Otherwise, stall at most once.
-  return sHasStalled.compareExchange(false, true) ? maxStall : doNotStall;
 #  endif
 }