Bug 1540587 - remove patch for 1539030 to fix decoding on additional tabs. r=jya

The patch for 1539030 didn't do what I'd hoped, and caused issues
with decoding av1 on additional tabs so I'm removing the "fix".

Differential Revision: https://phabricator.services.mozilla.com/D25627

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

dom/ipc/ContentChild.cpp

@@ -1173,9 +1173,7 @@ void ContentChild::LaunchRDDProcess() {
         nsresult rv;
         Endpoint<PRemoteDecoderManagerChild> endpoint;
         Unused << SendLaunchRDDProcess(&rv, &endpoint);
-        // Only call InitForContent if we got a valid enpoint back which
-        // indicates we needed to launch an RDD process.
-        if (rv == NS_OK && endpoint.IsValid()) {
+        if (rv == NS_OK) {
           RemoteDecoderManagerChild::InitForContent(std::move(endpoint));
         }
       }));

dom/ipc/ContentParent.cpp

@@ -1068,14 +1068,6 @@ mozilla::ipc::IPCResult ContentParent::RecvLaunchRDDProcess(
       Preferences::GetBool("media.rdd-process.enabled", false)) {
     RDDProcessManager* rdd = RDDProcessManager::Get();
     if (rdd) {
-      // If there is already an RDDChild, then we've already launched the
-      // RDD process.  We don't need to do anything else.  Specifically,
-      // we want to avoid calling CreateContentBridge again because that
-      // causes the RemoteDecoderManagerParent to rebuild needlessly.
-      if (rdd->GetRDDChild()) {
-        return IPC_OK();
-      }
-
       rdd->LaunchRDDProcess();
 
       bool rddOpened = rdd->CreateContentBridge(OtherPid(), aEndpoint);