Bug 1671773: Add ContentParent to ContentProcessManager before we call InitInternal. r=nika

Otherwise, if we return early, it will never get added, and we will crash when
trying to remove it when it's destroyed.

Differential Revision: https://phabricator.services.mozilla.com/D94487

dom/ipc/ContentParent.cpp

@@ -2414,6 +2414,9 @@ bool ContentParent::LaunchSubprocessResolve(bool aIsSync,
   base::ProcessId procId =
       base::GetProcId(mSubprocess->GetChildProcessHandle());
   Open(mSubprocess->TakeChannel(), procId);
+
+  ContentProcessManager::GetSingleton()->AddContentProcess(this);
+
 #ifdef MOZ_CODE_COVERAGE
   Unused << SendShareCodeCoverageMutex(
       CodeCoverageHandler::Get()->GetMutexHandle(procId));
@@ -2428,8 +2431,6 @@ bool ContentParent::LaunchSubprocessResolve(bool aIsSync,
     return false;
   }
 
-  ContentProcessManager::GetSingleton()->AddContentProcess(this);
-
   mHangMonitorActor = ProcessHangMonitor::AddProcess(this);
 
   // Set a reply timeout for CPOWs.