Bug 893242 - Part 3: Add ContentParent::GetAllEvenIfDead(). r=bent

To do this, we got rid of the explicit removal of a ContentParent from
sContentParents in MarkAsDead().  Instead, we rely on
LinkedListElement's destructor to remove the ContentParent from
sContentParents.

Thus, a ContentParent stays in sContentParents until it's destructed.
ContentParent::GetAll() checks whether the ContentParent is still alive,
so its behavior is unchanged.

dom/ipc/ContentParent.cpp

@@ -519,6 +519,23 @@ ContentParent::GetAll(nsTArray<ContentParent*>& aArray)
         return;
     }
 
+    for (ContentParent* cp = sContentParents->getFirst(); cp;
+         cp = cp->getNext()) {
+        if (cp->mIsAlive) {
+            aArray.AppendElement(cp);
+        }
+    }
+}
+
+void
+ContentParent::GetAllEvenIfDead(nsTArray<ContentParent*>& aArray)
+{
+    aArray.Clear();
+
+    if (!sContentParents) {
+        return;
+    }
+
     for (ContentParent* cp = sContentParents->getFirst(); cp;
          cp = cp->getNext()) {
         aArray.AppendElement(cp);
@@ -788,11 +805,6 @@ ContentParent::MarkAsDead()
     }
 
     mIsAlive = false;
-
-    // Remove from sContentParents.
-    if (isInList()) {
-         remove();
-    }
 }
 
 void

dom/ipc/ContentParent.h

@@ -106,6 +106,7 @@ public:
                        nsIDOMElement* aFrameElement);
 
     static void GetAll(nsTArray<ContentParent*>& aArray);
+    static void GetAllEvenIfDead(nsTArray<ContentParent*>& aArray);
 
     NS_DECL_ISUPPORTS
     NS_DECL_NSIOBSERVER