Bug 1429945 - Make ghost window unlinker e10s compatible. r=smaug

Content processes can contain ghost windows, so the debug-only ghost
window unlinker needs to send a message to child processes to get them
to run it, too.

MozReview-Commit-ID: 9Ffc3SDNDJB

--HG--
extra : rebase_source : 875891e9332cf41c4157d246b71c2c361cab4aa6

dom/ipc/ContentChild.cpp

@@ -137,6 +137,7 @@
 #ifdef NS_PRINTING
 #include "nsPrintingProxy.h"
 #endif
+#include "nsWindowMemoryReporter.h"
 
 #include "IHistory.h"
 #include "nsNetUtil.h"
@@ -2654,6 +2655,15 @@ ContentChild::RecvCycleCollect()
   return IPC_OK();
 }
 
+mozilla::ipc::IPCResult
+ContentChild::RecvUnlinkGhosts()
+{
+#ifdef DEBUG
+  nsWindowMemoryReporter::UnlinkGhostWindows();
+#endif
+  return IPC_OK();
+}
+
 mozilla::ipc::IPCResult
 ContentChild::RecvAppInfo(const nsCString& version, const nsCString& buildID,
                           const nsCString& name, const nsCString& UAName,

dom/ipc/ContentChild.h

@@ -410,6 +410,7 @@ public:
 
   virtual mozilla::ipc::IPCResult RecvGarbageCollect() override;
   virtual mozilla::ipc::IPCResult RecvCycleCollect() override;
+  virtual mozilla::ipc::IPCResult RecvUnlinkGhosts() override;
 
   virtual mozilla::ipc::IPCResult RecvAppInfo(const nsCString& version, const nsCString& buildID,
                                               const nsCString& name, const nsCString& UAName,

dom/ipc/ContentParent.cpp

@@ -578,6 +578,7 @@ static const char* sObserverTopics[] = {
   "child-gc-request",
   "child-cc-request",
   "child-mmu-request",
+  "child-ghost-request",
   "last-pb-context-exited",
   "file-watcher-update",
 #ifdef ACCESSIBILITY
@@ -2848,6 +2849,9 @@ ContentParent::Observe(nsISupports* aSubject,
   else if (!strcmp(aTopic, "child-mmu-request")){
     Unused << SendMinimizeMemoryUsage();
   }
+  else if (!strcmp(aTopic, "child-ghost-request")){
+    Unused << SendUnlinkGhosts();
+  }
   else if (!strcmp(aTopic, "last-pb-context-exited")) {
     Unused << SendLastPrivateDocShellDestroyed();
   }

dom/ipc/PContent.ipdl

@@ -455,6 +455,7 @@ child:
 
     async GarbageCollect();
     async CycleCollect();
+    async UnlinkGhosts();
 
     /**
      * Start accessibility engine in content process.

js/xpconnect/src/XPCComponents.cpp

@@ -2457,6 +2457,14 @@ nsXPCComponents_Utils::UnlinkGhostWindows()
 {
 #ifdef DEBUG
     nsWindowMemoryReporter::UnlinkGhostWindows();
+
+    if (XRE_IsParentProcess()) {
+        nsCOMPtr<nsIObserverService> obsvc = services::GetObserverService();
+        if (obsvc) {
+            obsvc->NotifyObservers(nullptr, "child-ghost-request", nullptr);
+        }
+    }
+
     return NS_OK;
 #else
     return NS_ERROR_NOT_IMPLEMENTED;