From cc533eaee5b800a534b93484598779debcdf5591 Mon Sep 17 00:00:00 2001
From: Gaming4JC <g4jc@hyperbola.info>
Date: Sat, 4 Jan 2020 19:48:30 -0500
Subject: Bug 1377993 - Make node slots less memory hungry in common cases.

Tag UXP Issue #1344
---
 dom/base/FragmentOrElement.h | 128 +++++++++++++++++++++++++++----------------
 1 file changed, 81 insertions(+), 47 deletions(-)

(limited to 'dom/base/FragmentOrElement.h')

diff --git a/dom/base/FragmentOrElement.h b/dom/base/FragmentOrElement.h
index a3a59ee43..4edd88908 100644
--- a/dom/base/FragmentOrElement.h
+++ b/dom/base/FragmentOrElement.h
@@ -15,6 +15,7 @@
 
 #include "mozilla/Attributes.h"
 #include "mozilla/MemoryReporting.h"
+#include "mozilla/UniquePtr.h"
 #include "nsAttrAndChildArray.h"          // member
 #include "nsCycleCollectionParticipant.h" // NS_DECL_CYCLE_*
 #include "nsIContent.h"                   // base class
@@ -239,8 +240,6 @@ protected:
   nsresult CopyInnerTo(FragmentOrElement* aDest);
 
 public:
-  // Because of a bug in MS C++ compiler nsDOMSlots must be declared public,
-  // otherwise nsXULElement::nsXULSlots doesn't compile.
   /**
    * There are a set of DOM- and scripting-specific instance variables
    * that may only be instantiated when a content object is accessed
@@ -249,29 +248,13 @@ public:
    * in a side structure that's only allocated when the content is
    * accessed through the DOM.
    */
-  class nsDOMSlots : public nsINode::nsSlots
+
+  class nsExtendedDOMSlots
   {
   public:
-    nsDOMSlots();
-    virtual ~nsDOMSlots();
-
-    void Traverse(nsCycleCollectionTraversalCallback &cb, bool aIsXUL);
-    void Unlink(bool aIsXUL);
-
-    size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const;
-
-    /**
-     * The .style attribute (an interface that forwards to the actual
-     * style rules)
-     * @see nsGenericHTMLElement::GetStyle
-     */
-    nsCOMPtr<nsICSSDeclaration> mStyle;
+    nsExtendedDOMSlots();
 
-    /**
-     * The .dataset attribute.
-     * @see nsGenericHTMLElement::GetDataset
-     */
-    nsDOMStringMap* mDataset; // [Weak]
+    ~nsExtendedDOMSlots();
 
     /**
      * SMIL Overridde style rules (for SMIL animation of CSS properties)
@@ -285,35 +268,17 @@ public:
     RefPtr<mozilla::DeclarationBlock> mSMILOverrideStyleDeclaration;
 
     /**
-     * An object implementing nsIDOMMozNamedAttrMap for this content (attributes)
-     * @see FragmentOrElement::GetAttributes
-     */
-    RefPtr<nsDOMAttributeMap> mAttributeMap;
-
-    union {
-      /**
-      * The nearest enclosing content node with a binding that created us.
-      * @see FragmentOrElement::GetBindingParent
-      */
-      nsIContent* mBindingParent;  // [Weak]
-
-      /**
-      * The controllers of the XUL Element.
-      */
-      nsIControllers* mControllers; // [OWNER]
-    };
+    * The nearest enclosing content node with a binding that created us.
+    * @see FragmentOrElement::GetBindingParent
+    */
+    nsIContent* mBindingParent;  // [Weak]
 
     /**
-     * An object implementing the .children property for this element.
-     */
-    RefPtr<nsContentList> mChildrenList;
+    * The controllers of the XUL Element.
+    */
+    nsCOMPtr<nsIControllers> mControllers;
 
     /**
-     * An object implementing the .classList property for this element.
-     */
-    RefPtr<nsDOMTokenList> mClassList;
-
-    /*
      * An object implementing the .labels property for this element.
      */
     RefPtr<nsLabelsNodeList> mLabelsList;
@@ -354,6 +319,55 @@ public:
      */
     nsDataHashtable<nsRefPtrHashKey<DOMIntersectionObserver>, int32_t> 
       mRegisteredIntersectionObservers;
+
+    /**
+     * For XUL to hold either frameloader or opener.
+     */
+    nsCOMPtr<nsISupports> mFrameLoaderOrOpener;
+
+  };
+
+  class nsDOMSlots : public nsINode::nsSlots
+  {
+  public:
+    nsDOMSlots();
+    virtual ~nsDOMSlots();
+
+    void Traverse(nsCycleCollectionTraversalCallback &cb);
+    void Unlink();
+
+    size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const;
+
+    /**
+     * The .style attribute (an interface that forwards to the actual
+     * style rules)
+     * @see nsGenericHTMLElement::GetStyle
+     */
+    nsCOMPtr<nsICSSDeclaration> mStyle;
+
+    /**
+     * The .dataset attribute.
+     * @see nsGenericHTMLElement::GetDataset
+     */
+    nsDOMStringMap* mDataset; // [Weak]
+
+    /**
+     * An object implementing nsIDOMMozNamedAttrMap for this content (attributes)
+     * @see FragmentOrElement::GetAttributes
+     */
+    RefPtr<nsDOMAttributeMap> mAttributeMap;
+
+    /**
+     * An object implementing the .children property for this element.
+     */
+    RefPtr<nsContentList> mChildrenList;
+
+    /**
+     * An object implementing the .classList property for this element.
+     */
+    RefPtr<nsDOMTokenList> mClassList;
+
+    mozilla::UniquePtr<nsExtendedDOMSlots> mExtendedSlots;
   };
 
 protected:
@@ -373,6 +387,26 @@ protected:
     return static_cast<nsDOMSlots*>(GetExistingSlots());
   }
 
+  nsExtendedDOMSlots* ExtendedDOMSlots()
+  {
+    nsDOMSlots* slots = DOMSlots();
+    if (!slots->mExtendedSlots) {
+      slots->mExtendedSlots = MakeUnique<nsExtendedDOMSlots>();
+    }
+
+    return slots->mExtendedSlots.get();
+  }
+
+  nsExtendedDOMSlots* GetExistingExtendedDOMSlots() const
+  {
+    nsDOMSlots* slots = GetExistingDOMSlots();
+    if (slots) {
+      return slots->mExtendedSlots.get();
+    }
+
+    return nullptr;
+  }
+
   /**
    * Calls SetIsElementInStyleScopeFlagOnSubtree for each shadow tree attached
    * to this node, which is assumed to be an Element.
-- 
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