Support optional parameter, |slotting|, in element.attachShadow

As the first step of implementing "Imperative Shadow DOM Distribution API",
this CL makes element.attachShadow take an optional parameter, |slotting|,
which should be 'manual' or 'auto'.

This CL also introduces new Runtime flag, ManualSlotting, to guard the new
feature.

BUG=869308

Change-Id: I71b115886c07c0090bef16b66da48c88e723a622
Reviewed-on: https://chromium-review.googlesource.com/1166767
Commit-Queue: Kyoko Muto <kymuto@google.com>
Reviewed-by: Hayato Ito <hayato@chromium.org>
Cr-Commit-Position: refs/heads/master@{#582524}

third_party/WebKit/LayoutTests/shadow-dom/imperative-api.html

@@ -6,23 +6,21 @@ See https://crbug.com/869308
 <script src="../resources/testharness.js"></script>
 <script src="../resources/testharnessreport.js"></script>
 <div id="host">
-  <div id="child1"></div>
+</div>
+<div id="host1">
 </div>
 
 <script>
 const host = document.querySelector('#host');
-const child1 = document.querySelector('#child1');
-const shadow_root = host.attachShadow({ mode: 'open', slotting: 'manual' });
-const slot1 = document.createElement('slot');
-shadow_root.appendChild(slot1);
+const host1 = document.querySelector('#host1');
 
 test(() => {
-  assert_equals(child1.assignedSlot, null);
-  assert_array_equals(slot1.assignedElements(), []);
-
-  slot1.assign([child1]);
-
-  assert_equals(child1.assignedSlot, slot1);
-  assert_array_equals(slot1.assignedElements(), [child1]);
-}, 'slot.assign(nodes) should work');
+  assert_not_equals(host.attachShadow({ mode: 'open', slotting: 'manual' }),
+                    null, 'slotting manual should work');
+  assert_not_equals(host1.attachShadow({ mode: 'open', slotting: 'auto' }),
+                    null, 'slotting auto should work');
+  assert_throws(new TypeError(), () => {
+    host.attachShadow({ mode: 'open', slotting: 'exceptional' })},
+                'others should throw exception');
+}, 'attachShadow can take slotting parameter');
 </script>

third_party/blink/renderer/core/dom/element.cc

@@ -2791,7 +2791,8 @@ ShadowRoot* Element::attachShadow(const ShadowRootInit& shadow_root_init_dict,
   DCHECK(!shadow_root_init_dict.hasMode() || !GetShadowRoot());
   bool delegates_focus = shadow_root_init_dict.hasDelegatesFocus() &&
                          shadow_root_init_dict.delegatesFocus();
-  return &AttachShadowRootInternal(type, delegates_focus);
+  bool manual_slotting = shadow_root_init_dict.slotting() == "manual";
+  return &AttachShadowRootInternal(type, delegates_focus, manual_slotting);
 }
 
 ShadowRoot& Element::CreateShadowRootInternal() {
@@ -2808,7 +2809,8 @@ ShadowRoot& Element::CreateUserAgentShadowRoot() {
 }
 
 ShadowRoot& Element::AttachShadowRootInternal(ShadowRootType type,
-                                              bool delegates_focus) {
+                                              bool delegates_focus,
+                                              bool manual_slotting) {
   // SVG <use> is a special case for using this API to create a closed shadow
   // root.
   DCHECK(CanAttachShadowRoot() || IsSVGUseElement(*this));
@@ -2819,6 +2821,8 @@ ShadowRoot& Element::AttachShadowRootInternal(ShadowRootType type,
   GetDocument().SetShadowCascadeOrder(ShadowCascadeOrder::kShadowCascadeV1);
   ShadowRoot& shadow_root = CreateAndAttachShadowRoot(type);
   shadow_root.SetDelegatesFocus(delegates_focus);
+  shadow_root.SetSlotting(manual_slotting ? ShadowRootSlotting::kManual
+                                          : ShadowRootSlotting::kAuto);
   return shadow_root;
 }
 

third_party/blink/renderer/core/dom/element.h

@@ -514,7 +514,8 @@ class CORE_EXPORT Element : public ContainerNode {
   }
   ShadowRoot& CreateUserAgentShadowRoot();
   ShadowRoot& AttachShadowRootInternal(ShadowRootType,
-                                       bool delegates_focus = false);
+                                       bool delegates_focus = false,
+                                       bool manual_slotting = false);
 
   // Returns the shadow root attached to this element if it is a shadow host.
   ShadowRoot* GetShadowRoot() const;

third_party/blink/renderer/core/dom/shadow_root.cc

@@ -74,6 +74,7 @@ ShadowRoot::ShadowRoot(Document& document, ShadowRootType type)
       type_(static_cast<unsigned short>(type)),
       registered_with_parent_shadow_root_(false),
       delegates_focus_(false),
+      slotting_(static_cast<unsigned short>(ShadowRootSlotting::kAuto)),
       needs_distribution_recalc_(false),
       unused_(0) {
   if (IsV0())

third_party/blink/renderer/core/dom/shadow_root.h

@@ -48,6 +48,8 @@ class WhitespaceAttacher;
 
 enum class ShadowRootType { V0, kOpen, kClosed, kUserAgent };
 
+enum class ShadowRootSlotting { kManual, kAuto };
+
 class CORE_EXPORT ShadowRoot final : public DocumentFragment, public TreeScope {
   DEFINE_WRAPPERTYPEINFO();
   USING_GARBAGE_COLLECTED_MIXIN(ShadowRoot);
@@ -156,6 +158,14 @@ class CORE_EXPORT ShadowRoot final : public DocumentFragment, public TreeScope {
   void SetDelegatesFocus(bool flag) { delegates_focus_ = flag; }
   bool delegatesFocus() const { return delegates_focus_; }
 
+  void SetSlotting(ShadowRootSlotting slotting) {
+    slotting_ = static_cast<unsigned short>(slotting);
+  }
+  bool IsManualSlotting() {
+    return slotting_ ==
+           static_cast<unsigned short>(ShadowRootSlotting::kManual);
+  }
+
   bool ContainsShadowRoots() const { return child_shadow_root_count_; }
 
   StyleSheetList& StyleSheets();
@@ -187,8 +197,9 @@ class CORE_EXPORT ShadowRoot final : public DocumentFragment, public TreeScope {
   unsigned short type_ : 2;
   unsigned short registered_with_parent_shadow_root_ : 1;
   unsigned short delegates_focus_ : 1;
+  unsigned short slotting_ : 1;
   unsigned short needs_distribution_recalc_ : 1;
-  unsigned short unused_ : 11;
+  unsigned short unused_ : 10;
 
   DISALLOW_COPY_AND_ASSIGN(ShadowRoot);
 };

third_party/blink/renderer/core/dom/shadow_root_init.idl

@@ -5,8 +5,10 @@
 // Spec: https://w3c.github.io/webcomponents/spec/shadow/#shadowrootinit-dictionary
 
 enum ShadowRootMode { "open", "closed" };
+enum ShadowRootSlottingMode { "manual", "auto" };
 
 dictionary ShadowRootInit {
     required ShadowRootMode mode;
     boolean delegatesFocus;
+    [RuntimeEnabled=ManualSlotting] ShadowRootSlottingMode slotting;
 };

third_party/blink/renderer/platform/runtime_enabled_features.json5

@@ -652,6 +652,10 @@
       origin_trial_feature_name: "LowLatencyCanvas",
       status: "experimental",
     },
+    {
+      name:"ManualSlotting",
+      status:"test",
+    },
     {
       name: "MediaCapabilities",
       origin_trial_feature_name: "MediaCapabilities",