Bug 1250820 - Part 4: Add MAX to CSSPseudoClassType. r=heycam

Just like CSSPseudoElementType, which uses a special type to represent the
maximum length. We can replace "CSSPseudoClassType::NotPseudo + 1" with
"CSSPseudoClassType::MAX", which means the maximum length.

MozReview-Commit-ID: 4xH0avpWPqX

--HG--
extra : rebase_source : bc8b6a5bb5a84782dea891054b8ea4c5d7ea3db8

layout/inspector/inDOMUtils.cpp

@@ -1205,7 +1205,7 @@ GetStatesForPseudoClass(const nsAString& aStatePseudo)
     EventStates()
   };
   static_assert(MOZ_ARRAY_LENGTH(sPseudoClassStates) ==
-                static_cast<size_t>(CSSPseudoClassType::NotPseudo) + 1,
+                static_cast<size_t>(CSSPseudoClassType::MAX),
                 "Length of PseudoClassStates array is incorrect");
 
   nsCOMPtr<nsIAtom> atom = NS_Atomize(aStatePseudo);

layout/style/nsCSSPseudoClasses.h

@@ -29,7 +29,8 @@ enum class CSSPseudoClassType : CSSPseudoClassTypeBase
 #include "nsCSSPseudoClassList.h"
 #undef CSS_PSEUDO_CLASS
   Count,
-  NotPseudo   // This value MUST be last! SelectorMatches depends on it.
+  NotPseudo,  // This value MUST be second last! SelectorMatches depends on it.
+  MAX
 };
 
 } // namespace mozilla

layout/style/nsCSSRuleProcessor.cpp

@@ -1621,8 +1621,8 @@ static const EventStates sPseudoClassStates[] = {
   EventStates()
 };
 static_assert(MOZ_ARRAY_LENGTH(sPseudoClassStates) ==
-              static_cast<size_t>(CSSPseudoClassType::NotPseudo) + 1,
-              "CSSPseudoClassType::NotPseudo is no longer at the end of"
+              static_cast<size_t>(CSSPseudoClassType::MAX),
+              "CSSPseudoClassType::MAX is no longer equal to the length of "
               "sPseudoClassStates");
 
 static bool