Simplify docs on MatchAuthorRules now that MatchScopedRules is gone.

Move the docs inline as method docs and just link from the md file.

Change-Id: I286db306b4f01553ac6fa09a271aa65457c76de8
Reviewed-on: https://chromium-review.googlesource.com/1011764Reviewed-by: Rune Lillesveen <futhark@chromium.org>
Commit-Queue: Fergal Daly <fergal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#550880}

third_party/blink/renderer/core/css/resolver/style_resolver.cc

@@ -186,6 +186,9 @@ static inline ScopedStyleResolver* ScopedResolverFor(const Element& element) {
   return tree_scope->GetScopedStyleResolver();
 }
 
+// Matches :host and :host-context rules if the element is a shadow host.
+// It matches rules from the ShadowHostRules of the ScopedStyleResolver
+// of the attached shadow root.
 static void MatchHostRules(const Element& element,
                            ElementRuleCollector& collector) {
   ShadowRoot* shadow_root = element.GetShadowRoot();
@@ -200,6 +203,10 @@ static void MatchHostRules(const Element& element,
   }
 }
 
+// Matches `::slotted` selectors. It matches rules in the element's slot's
+// scope. If that slot is itself slotted it will match rules in the slot's
+// slot's scope and so on. The result is that it considers a chain of scopes
+// descending from the element's own scope.
 static void MatchSlottedRules(const Element& element,
                               ElementRuleCollector& collector) {
   HTMLSlotElement* slot = element.AssignedSlot();
@@ -220,6 +227,8 @@ static void MatchSlottedRules(const Element& element,
   }
 }
 
+// Matches rules from the element's scope. The selectors may cross shadow
+// boundaries during matching, like for :host-context.
 static void MatchElementScopeRules(const Element& element,
                                    ScopedStyleResolver* element_scope_resolver,
                                    ElementRuleCollector& collector) {

third_party/blink/renderer/core/css/resolver/style_resolver.h

@@ -165,6 +165,8 @@ class CORE_EXPORT StyleResolver final
   void MatchRuleSet(ElementRuleCollector&, RuleSet*);
   void MatchUARules(ElementRuleCollector&);
   void MatchUserRules(ElementRuleCollector&);
+  // This matches `::part` selectors. It looks in ancestor scopes as far as
+  // part mapping requires.
   void MatchPseudoPartRules(const Element&, ElementRuleCollector&);
   void MatchScopedRulesV0(const Element&,
                           ElementRuleCollector&,

third_party/blink/renderer/core/css/style-calculation.md

@@ -148,39 +148,13 @@ which matches the rules from the
     [`MatchAuthorRules`](https://cs.chromium.org/?q=symbol:%5Eblink::StyleResolver::MatchAuthorRules$)
 
 [`MatchAuthorRules`](https://cs.chromium.org/?q=symbol:%5Eblink::StyleResolver::MatchAuthorRules$)
-splits into two cases.
+splits applies the following steps (read the method docs):
 
+- [`MatchHostRules`](https://cs.chromium.org/?q=symbol:%5Eblink::MatchHostRules$)
+- [`MatchSlottedRules`](https://cs.chromium.org/?q=symbol:%5Eblink::MatchSlottedRules$)
+- [`MatchElementScopeRules`](https://cs.chromium.org/?q=symbol:%5Eblink::MatchElementScopeRules$)
+- [`MatchPseudoPartRules`](https://cs.chromium.org/?q=symbol:%5Eblink::StyleResolver::MatchPseudoPartRules$)
 
-#### [`MatchHostRules`](https://cs.chromium.org/?q=symbol:%5Eblink::MatchHostRules$)
-
-This method matches :host and :host-context rules for shadow host elements.
-This does nothing if the element in question is not a shadow host.
-If it is a shadow host,
-it examines the `ScopedStyleResolver` of its shadow root.
-Any host related rules will be in the `ShadowHostRules` list of that `ScopedStyleResolver`
-
-
-#### [`MatchScopedRules`](https://cs.chromium.org/?q=symbol:%5Eblink::StyleResolver::MatchScopedRules$)
-
-For V1 Shadow DOM, this simply calls 3 functions explained below.
-
-##### ['MatchSlottedRules'](https://cs.chromium.org/?q=symbol:%5Eblink::MatchSlottedRules)
-
-This matches `::slotted` selectors.
-It matches rules in the element's slot's scope.
-If that slot is itself slotted it will match rules in the slot's slot's scope and so on.
-The result is that it considers a chain of scopes descending from the element's own scope.
-
-##### ['MatchElementScopeRules'](https://cs.chromium.org/?q=symbol:%5Eblink::MatchElementScopeRules)
-
-This matches rules from the element's scope.
-The selectors may cross shadow boundaries during matching,
-like for :host-context.
-
-##### ['MatchPseudoPartRules'](https://cs.chromium.org/?q=symbol:%5Eblink::StyleResolver::MatchPseudoPartRules)
-
-This matches `::part` selectors.
-It looks in ancestor scopes as far as part mapping requires.
 
 #### <a name="CollectMatchingRulesForList"></a>[`CollectMatchingRulesForList`](https://cs.chromium.org/?q=symbol:%5Eblink::ElementRuleCollector::CollectMatchingRulesForList$) - testing some rules against an element