Bug 1591891 - Make the fix for bug 1536468 work with session history in the parent turned off. r=annyG

Differential Revision: https://phabricator.services.mozilla.com/D50786

--HG--
extra : rebase_source : 10199c278de3618e17497dc361d66262223c462d
extra : source : cc77b3f6df12a3a2105941402bce9fedbacf255c
extra : histedit_source : d4feddbc8a9dad5f9fab3860120d71b510e96ab6

dom/webbrowserpersist/PWebBrowserPersistDocument.ipdl

@@ -18,6 +18,11 @@ using refcounted class nsIReferrerInfo from "mozilla/dom/ReferrerInfoUtils.h";
 
 namespace mozilla {
 
+union SessionHistoryEntryOrCacheKey {
+  nullable PSHEntry;
+  uint32_t;
+};
+
 // nsIWebBrowserPersistDocument has attributes which can be read
 // synchronously.  To avoid using sync IPC for them, the actor sends
 // this structure from the child to the parent before the parent actor
@@ -31,7 +36,7 @@ struct WebBrowserPersistDocumentAttrs {
   nsString title;
   nsIReferrerInfo referrerInfo;
   nsString contentDisposition;
-  nullable PSHEntry sessionHistoryEntry;
+  SessionHistoryEntryOrCacheKey sessionHistoryEntryOrCacheKey;
   uint32_t persistFlags;
   PrincipalInfo principal;
 };

dom/webbrowserpersist/WebBrowserPersistDocumentChild.cpp

@@ -14,6 +14,7 @@
 #include "WebBrowserPersistResourcesChild.h"
 #include "WebBrowserPersistSerializeChild.h"
 #include "SHEntryChild.h"
+#include "mozilla/StaticPrefs_fission.h"
 
 namespace mozilla {
 
@@ -57,10 +58,14 @@ void WebBrowserPersistDocumentChild::Start(
   ENSURE(aDocument->GetTitle(attrs.title()));
   ENSURE(aDocument->GetContentDisposition(attrs.contentDisposition()));
 
-  RefPtr<dom::SHEntryChild> shEntryChild =
-      aDocument->GetHistory().downcast<dom::SHEntryChild>();
-  if (shEntryChild) {
-    attrs.sessionHistoryEntryChild() = shEntryChild.get();
+  // shEntryChild needs to remain in scope until after the SendAttributes call,
+  // to keep the actor alive.
+  RefPtr<dom::SHEntryChild> shEntryChild;
+  if (StaticPrefs::fission_sessionHistoryInParent()) {
+    shEntryChild = aDocument->GetHistory().downcast<dom::SHEntryChild>();
+    attrs.sessionHistoryEntryOrCacheKey() = shEntryChild;
+  } else {
+    attrs.sessionHistoryEntryOrCacheKey() = aDocument->GetCacheKey();
   }
 
   ENSURE(aDocument->GetPersistFlags(&(attrs.persistFlags())));

dom/webbrowserpersist/WebBrowserPersistRemoteDocument.cpp

@@ -24,9 +24,12 @@ WebBrowserPersistRemoteDocument ::WebBrowserPersistRemoteDocument(
     : mActor(aActor), mAttrs(aAttrs), mPostData(aPostData) {
   nsresult rv;
   mPrincipal = ipc::PrincipalInfoToPrincipal(mAttrs.principal(), &rv);
-  mSHEntry =
-      static_cast<dom::SHEntryParent*>(mAttrs.sessionHistoryEntryParent())
-          ->GetSHEntry();
+  if (mAttrs.sessionHistoryEntryOrCacheKey().type() ==
+      SessionHistoryEntryOrCacheKey::TPSHEntryParent) {
+    mSHEntry = static_cast<dom::SHEntryParent*>(
+                   mAttrs.sessionHistoryEntryOrCacheKey().get_PSHEntryParent())
+                   ->GetSHEntry();
+  }
 }
 
 WebBrowserPersistRemoteDocument::~WebBrowserPersistRemoteDocument() {
@@ -93,8 +96,13 @@ WebBrowserPersistRemoteDocument::GetContentDisposition(nsAString& aDisp) {
 NS_IMETHODIMP
 WebBrowserPersistRemoteDocument::GetCacheKey(uint32_t* aCacheKey) {
   *aCacheKey = 0;
-  if (mSHEntry) {
-    *aCacheKey = mSHEntry->GetCacheKey();
+  if (mAttrs.sessionHistoryEntryOrCacheKey().type() ==
+      SessionHistoryEntryOrCacheKey::TPSHEntryParent) {
+    if (mSHEntry) {
+      *aCacheKey = mSHEntry->GetCacheKey();
+    }
+  } else {
+    *aCacheKey = mAttrs.sessionHistoryEntryOrCacheKey();
   }
   return NS_OK;
 }

dom/webbrowserpersist/nsIWebBrowserPersistDocument.idl

@@ -72,6 +72,7 @@ interface nsIWebBrowserPersistDocument : nsISupports
    * The cache key.  Unlike in nsISHEntry, where it's wrapped in an
    * nsISupportsPRUint32, this is just the integer.
    */
+  [infallible]
   readonly attribute unsigned long cacheKey;
 
   /**