Optimize bit access for hot code path in IsHTMLElement()

The [1] CL combined the ElementNamespaceType bits, to save
space. However, as seen in [2], this caused a performance
regression, likely due to a slower IsHTMLElement(). This CL
attempts to get back that performance through two optimizations:
 - ALWAYS_INLINE the accessors for both GetElementNamespaceType()
   and the IsXyzElement() accessors.
 - Move kHTML to a value of 0, in the hope that this operation
   is faster when the kConstant is zero:
      GetElementNamespaceType() == kConstant

[1] https://chromium.googlesource.com/chromium/src/+/956931765e5969c44ad9a4641ff1c99977c8498f
[2] https://crbug.com/1036543

Bug: 1036543
Change-Id: I4976829ab0b7c9d875d4d4e6b516333b44e7dddb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2029311
Commit-Queue: Kent Tamura <tkent@chromium.org>
Auto-Submit: Mason Freed <masonfreed@chromium.org>
Reviewed-by: Kent Tamura <tkent@chromium.org>
Cr-Commit-Position: refs/heads/master@{#737181}

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

@@ -278,13 +278,13 @@ class CORE_EXPORT Node : public EventTarget {
     return GetDOMNodeType() == DOMNodeType::kDocumentFragment;
   }
 
-  bool IsHTMLElement() const {
+  ALWAYS_INLINE bool IsHTMLElement() const {
     return GetElementNamespaceType() == ElementNamespaceType::kHTML;
   }
-  bool IsMathMLElement() const {
+  ALWAYS_INLINE bool IsMathMLElement() const {
     return GetElementNamespaceType() == ElementNamespaceType::kMathML;
   }
-  bool IsSVGElement() const {
+  ALWAYS_INLINE bool IsSVGElement() const {
     return GetElementNamespaceType() == ElementNamespaceType::kSVG;
   }
 
@@ -989,35 +989,42 @@ class CORE_EXPORT Node : public EventTarget {
   }
 
   enum class ElementNamespaceType : uint32_t {
-    kOther = 0,
-    kHTML = 1 << kElementNamespaceTypeShift,
-    kMathML = 2 << kElementNamespaceTypeShift,
-    kSVG = 3 << kElementNamespaceTypeShift,
+    kHTML = 0,
+    kMathML = 1 << kElementNamespaceTypeShift,
+    kSVG = 2 << kElementNamespaceTypeShift,
+    kOther = 3 << kElementNamespaceTypeShift,
   };
-  ElementNamespaceType GetElementNamespaceType() const {
+  ALWAYS_INLINE ElementNamespaceType GetElementNamespaceType() const {
     return static_cast<ElementNamespaceType>(node_flags_ &
                                              kElementNamespaceTypeMask);
   }
 
  protected:
   enum ConstructionType {
-    kCreateOther =
-        kDefaultNodeFlags | static_cast<NodeFlags>(DOMNodeType::kOther),
-    kCreateText =
-        kDefaultNodeFlags | static_cast<NodeFlags>(DOMNodeType::kText),
-    kCreateContainer = kDefaultNodeFlags | kIsContainerFlag,
+    kCreateOther = kDefaultNodeFlags |
+                   static_cast<NodeFlags>(DOMNodeType::kOther) |
+                   static_cast<NodeFlags>(ElementNamespaceType::kOther),
+    kCreateText = kDefaultNodeFlags |
+                  static_cast<NodeFlags>(DOMNodeType::kText) |
+                  static_cast<NodeFlags>(ElementNamespaceType::kOther),
+    kCreateContainer = kDefaultNodeFlags | kIsContainerFlag |
+                       static_cast<NodeFlags>(ElementNamespaceType::kOther),
     kCreateElement =
         kCreateContainer | static_cast<NodeFlags>(DOMNodeType::kElement),
     kCreateDocumentFragment =
         kCreateContainer |
         static_cast<NodeFlags>(DOMNodeType::kDocumentFragment),
     kCreateShadowRoot = kCreateDocumentFragment | kIsInShadowTreeFlag,
-    kCreateHTMLElement =
-        kCreateElement | static_cast<NodeFlags>(ElementNamespaceType::kHTML),
+    kCreateHTMLElement = kDefaultNodeFlags | kIsContainerFlag |
+                         static_cast<NodeFlags>(DOMNodeType::kElement) |
+                         static_cast<NodeFlags>(ElementNamespaceType::kHTML),
     kCreateMathMLElement =
-        kCreateElement | static_cast<NodeFlags>(ElementNamespaceType::kMathML),
-    kCreateSVGElement =
-        kCreateElement | static_cast<NodeFlags>(ElementNamespaceType::kSVG),
+        kDefaultNodeFlags | kIsContainerFlag |
+        static_cast<NodeFlags>(DOMNodeType::kElement) |
+        static_cast<NodeFlags>(ElementNamespaceType::kMathML),
+    kCreateSVGElement = kDefaultNodeFlags | kIsContainerFlag |
+                        static_cast<NodeFlags>(DOMNodeType::kElement) |
+                        static_cast<NodeFlags>(ElementNamespaceType::kSVG),
     kCreateDocument = kCreateContainer | kIsConnectedFlag,
     kCreateV0InsertionPoint = kCreateHTMLElement | kIsV0InsertionPointFlag,
     kCreateEditingText = kCreateText | kHasNameOrIsEditingTextFlag,