Bug 1431272 - Set the process priority for the preallocated process when it becomes active. r=jimm

This is currently a no-op, but the idea here is to make sure to set the
process to "active" when we're about to use it for something.

MozReview-Commit-ID: 2QUlALhfD4k

--HG--
extra : rebase_source : 13a67e9353bb47593b1394ce7ae7a7b6eef6e381

dom/ipc/ContentParent.cpp

@@ -2833,6 +2833,10 @@ ContentParent::Observe(nsISupports* aSubject,
 {
   if (mSubprocess && (!strcmp(aTopic, "profile-before-change") ||
                       !strcmp(aTopic, "xpcom-shutdown"))) {
+    // Make sure that our process will get scheduled.
+    ProcessPriorityManager::SetProcessPriority(this,
+                                               PROCESS_PRIORITY_FOREGROUND);
+
     // Okay to call ShutDownProcess multiple times.
     ShutDownProcess(SEND_SHUTDOWN_MESSAGE);
 

dom/ipc/PreallocatedProcessManager.cpp

@@ -168,6 +168,8 @@ PreallocatedProcessManagerImpl::Take()
 
   if (mPreallocatedProcess) {
     // The preallocated process is taken. Let's try to start up a new one soon.
+    ProcessPriorityManager::SetProcessPriority(mPreallocatedProcess,
+                                               PROCESS_PRIORITY_FOREGROUND);
     AllocateOnIdle();
   }