Bug 1567094 - Make GetVisitedDependentColor const-friendly. r=jrmuizel

Differential Revision: https://phabricator.services.mozilla.com/D41934

--HG--
extra : moz-landing-system : lando

layout/style/ComputedStyle.cpp

@@ -264,14 +264,14 @@ void ComputedStyle::List(FILE* out, int32_t aIndent) {
 #endif
 
 template <typename Func>
-static nscolor GetVisitedDependentColorInternal(ComputedStyle* aSc,
+static nscolor GetVisitedDependentColorInternal(const ComputedStyle& aStyle,
                                                 Func aColorFunc) {
   nscolor colors[2];
-  colors[0] = aColorFunc(aSc);
-  if (ComputedStyle* visitedStyle = aSc->GetStyleIfVisited()) {
-    colors[1] = aColorFunc(visitedStyle);
+  colors[0] = aColorFunc(aStyle);
+  if (const ComputedStyle* visitedStyle = aStyle.GetStyleIfVisited()) {
+    colors[1] = aColorFunc(*visitedStyle);
     return ComputedStyle::CombineVisitedColors(colors,
-                                               aSc->RelevantLinkVisited());
+                                               aStyle.RelevantLinkVisited());
   }
   return colors[0];
 }
@@ -306,14 +306,14 @@ static nscolor ExtractColor(const ComputedStyle& aStyle,
 #define STYLE_FIELD(struct_, field_) aField == &struct_::field_ ||
 #define STYLE_STRUCT(name_, fields_)                                           \
   template <>                                                                  \
-  nscolor ComputedStyle::GetVisitedDependentColor(                             \
-      decltype(nsStyle##name_::MOZ_ARG_1 fields_) nsStyle##name_::*aField) {   \
+  nscolor ComputedStyle::GetVisitedDependentColor(decltype(                    \
+      nsStyle##name_::MOZ_ARG_1 fields_) nsStyle##name_::*aField) const {      \
     MOZ_ASSERT(MOZ_FOR_EACH(STYLE_FIELD, (nsStyle##name_, ), fields_) false,   \
                "Getting visited-dependent color for a field in nsStyle" #name_ \
                " which is not listed in nsCSSVisitedDependentPropList.h");     \
     return GetVisitedDependentColorInternal(                                   \
-        this, [aField](ComputedStyle* sc) {                                    \
-          return ExtractColor(*sc, sc->Style##name_()->*aField);               \
+        *this, [aField](const ComputedStyle& aStyle) {                         \
+          return ExtractColor(aStyle, aStyle.Style##name_()->*aField);         \
         });                                                                    \
   }
 #include "nsCSSVisitedDependentPropList.h"

layout/style/ComputedStyle.h

@@ -254,7 +254,7 @@ class ComputedStyle {
    *               been listed in nsCSSVisitedDependentPropList.h.
    */
   template <typename T, typename S>
-  nscolor GetVisitedDependentColor(T S::*aField);
+  nscolor GetVisitedDependentColor(T S::*aField) const;
 
   /**
    * aColors should be a two element array of nscolor in which the first