7 files changed, 58 insertions, 16 deletions
diff --git a/layout/base/nsCSSFrameConstructor.cpp b/layout/base/nsCSSFrameConstructor.cpp
index b40e6f8b61..9a0410d737 100644
--- a/layout/base/nsCSSFrameConstructor.cpp
+++ b/layout/base/nsCSSFrameConstructor.cpp
@@ -3580,6 +3580,10 @@ nsCSSFrameConstructor::FindHTMLData(Element* aElement,
     return nullptr;
   }
 
+  if (aTag == nsGkAtoms::details && !HTMLDetailsElement::IsDetailsEnabled()) {
+    return nullptr;
+  }
+
   static const FrameConstructionDataByTag sHTMLData[] = {
     SIMPLE_TAG_CHAIN(img, nsCSSFrameConstructor::FindImgData),
     SIMPLE_TAG_CHAIN(mozgeneratedcontentimage,
@@ -5791,7 +5795,7 @@ nsCSSFrameConstructor::AddFrameConstructionItemsInternal(nsFrameConstructorState
   // ::before and ::after); we always want to create "internal" anonymous
   // content.
   auto* details = HTMLDetailsElement::FromContentOrNull(parent);
-  if (details && !details->Open() &&
+  if (details && details->IsDetailsEnabled() && !details->Open() &&
       (!aContent->IsRootOfNativeAnonymousSubtree() ||
        aContent->IsGeneratedContentContainerForBefore() ||
        aContent->IsGeneratedContentContainerForAfter())) {
@@ -5959,7 +5963,7 @@ nsCSSFrameConstructor::AddFrameConstructionItemsInternal(nsFrameConstructorState
   }
 
   FrameConstructionItem* item = nullptr;
-  if (details && details->Open()) {
+  if (details && details->IsDetailsEnabled() && details->Open()) {
     auto* summary = HTMLSummaryElement::FromContentOrNull(aContent);
     if (summary && summary->IsMainSummary()) {
       // If details is open, the main summary needs to be rendered as if it is
diff --git a/layout/generic/crashtests/crashtests.list b/layout/generic/crashtests/crashtests.list
index d44d7614c1..c8fb84feb9 100644
--- a/layout/generic/crashtests/crashtests.list
+++ b/layout/generic/crashtests/crashtests.list
@@ -606,19 +606,19 @@ pref(layout.css.grid.enabled,true) load 1225376.html
 pref(layout.css.grid.enabled,true) load 1225592.html
 load 1229437-1.html
 load 1229437-2.html
-load details-containing-only-text.html
-load details-display-none-summary-1.html
-load details-display-none-summary-2.html
-load details-display-none-summary-3.html
-load details-open-overflow-auto.html
-load details-open-overflow-hidden.html
-load details-three-columns.html
+pref(dom.details_element.enabled,true) load details-containing-only-text.html
+pref(dom.details_element.enabled,true) load details-display-none-summary-1.html
+pref(dom.details_element.enabled,true) load details-display-none-summary-2.html
+pref(dom.details_element.enabled,true) load details-display-none-summary-3.html
+pref(dom.details_element.enabled,true) load details-open-overflow-auto.html
+pref(dom.details_element.enabled,true) load details-open-overflow-hidden.html
+pref(dom.details_element.enabled,true) load details-three-columns.html
 load first-letter-638937-1.html
 load first-letter-638937-2.html
 load flex-nested-abspos-1.html
 pref(dom.meta-viewport.enabled,true) test-pref(font.size.inflation.emPerLine,15) asserts(0-100) load font-inflation-762332.html # bug 762332
 load outline-on-frameset.xhtml
-load summary-position-out-of-flow.html
+pref(dom.details_element.enabled,true) load summary-position-out-of-flow.html
 load text-overflow-bug666751-1.html
 load text-overflow-bug666751-2.html
 load text-overflow-bug670564.xhtml
diff --git a/layout/generic/nsContainerFrame.cpp b/layout/generic/nsContainerFrame.cpp
index 835ba9b262..47afed9de1 100644
--- a/layout/generic/nsContainerFrame.cpp
+++ b/layout/generic/nsContainerFrame.cpp
@@ -1891,10 +1891,12 @@ nsContainerFrame::RenumberFrameAndDescendants(int32_t* aOrdinal,
   }
 
   // Do not renumber list for summary elements.
-  HTMLSummaryElement* summary =
-    HTMLSummaryElement::FromContent(kid->GetContent());
-  if (summary && summary->IsMainSummary()) {
-    return false;
+  if (HTMLDetailsElement::IsDetailsEnabled()) {
+    HTMLSummaryElement* summary =
+      HTMLSummaryElement::FromContent(kid->GetContent());
+    if (summary && summary->IsMainSummary()) {
+      return false;
+    }
   }
 
   bool kidRenumberedABullet = false;
diff --git a/layout/reftests/details-summary/disabled-no-summary-ref.html b/layout/reftests/details-summary/disabled-no-summary-ref.html
new file mode 100644
index 0000000000..6ecdbcdc0a
--- /dev/null
+++ b/layout/reftests/details-summary/disabled-no-summary-ref.html
@@ -0,0 +1,11 @@
+<!DOCTYPE html>
+<!-- Any copyright is dedicated to the Public Domain.
+   - http://creativecommons.org/publicdomain/zero/1.0/ -->
+
+<html>
+  <body>
+    <div>
+      <p>This is the details.</p>
+    </div>
+  </body>
+</html>
diff --git a/layout/reftests/details-summary/disabled-single-summary-ref.html b/layout/reftests/details-summary/disabled-single-summary-ref.html
new file mode 100644
index 0000000000..f643af6dcd
--- /dev/null
+++ b/layout/reftests/details-summary/disabled-single-summary-ref.html
@@ -0,0 +1,12 @@
+<!DOCTYPE html>
+<!-- Any copyright is dedicated to the Public Domain.
+   - http://creativecommons.org/publicdomain/zero/1.0/ -->
+
+<html>
+  <body>
+    <div>
+      <div>Summary</div>
+      <p>This is the details.</p>
+    </div>
+  </body>
+</html>
diff --git a/layout/reftests/details-summary/reftest.list b/layout/reftests/details-summary/reftest.list
index a972cf4980..6b558ea137 100644
--- a/layout/reftests/details-summary/reftest.list
+++ b/layout/reftests/details-summary/reftest.list
@@ -1,3 +1,10 @@
+default-preferences pref(dom.details_element.enabled,true)
+
+# Disable <details> and <summary>
+pref(dom.details_element.enabled,false) == single-summary.html disabled-single-summary-ref.html
+pref(dom.details_element.enabled,false) == open-single-summary.html disabled-single-summary-ref.html
+pref(dom.details_element.enabled,false) == no-summary.html disabled-no-summary-ref.html
+
 # Basic <summary> handling
 == multiple-summary.html single-summary.html
 == open-multiple-summary.html open-multiple-summary-ref.html
diff --git a/layout/style/nsLayoutStylesheetCache.cpp b/layout/style/nsLayoutStylesheetCache.cpp
index bf87b006ca..1905d8c5cd 100644
--- a/layout/style/nsLayoutStylesheetCache.cpp
+++ b/layout/style/nsLayoutStylesheetCache.cpp
@@ -121,6 +121,11 @@ nsLayoutStylesheetCache::UASheet()
 StyleSheet*
 nsLayoutStylesheetCache::HTMLSheet()
 {
+  if (!mHTMLSheet) {
+    LoadSheetURL("resource://gre-resources/html.css",
+                 &mHTMLSheet, eAgentSheetFeatures, eCrash);
+  }
+
   return mHTMLSheet;
 }
 
@@ -316,8 +321,6 @@ nsLayoutStylesheetCache::nsLayoutStylesheetCache(StyleBackendType aType)
   // per-profile, since they're profile-invariant.
   LoadSheetURL("resource://gre-resources/counterstyles.css",
                &mCounterStylesSheet, eAgentSheetFeatures, eCrash);
-  LoadSheetURL("resource://gre-resources/html.css",
-               &mHTMLSheet, eAgentSheetFeatures, eCrash);
   LoadSheetURL("chrome://global/content/minimal-xul.css",
                &mMinimalXULSheet, eAgentSheetFeatures, eCrash);
   LoadSheetURL("resource://gre-resources/quirk.css",
@@ -378,6 +381,8 @@ nsLayoutStylesheetCache::For(StyleBackendType aType)
     //                               "layout.css.example-pref.enabled");
     Preferences::RegisterCallback(&DependentPrefChanged,
                                   "layout.css.grid.enabled");
+    Preferences::RegisterCallback(&DependentPrefChanged,
+                                  "dom.details_element.enabled");
   }
 
   return cache;
@@ -549,6 +554,7 @@ nsLayoutStylesheetCache::DependentPrefChanged(const char* aPref, void* aData)
                   gStyleCache_Servo ? &gStyleCache_Servo->sheet_ : nullptr);
 
   INVALIDATE(mUASheet);  // for layout.css.grid.enabled
+  INVALIDATE(mHTMLSheet); // for dom.details_element.enabled
 
 #undef INVALIDATE
 }