Bug 1633448: part 1) Move `Selection::SubtractRange` to `StyledRanges`. r=smaug

`StyledRanges should have as few dependencies to `Selection` as
possible.

Differential Revision: https://phabricator.services.mozilla.com/D72688

dom/base/Selection.cpp

@@ -729,8 +729,9 @@ int32_t Selection::StyledRanges::FindInsertionPoint(
 //    difference to aOutput. It is assumed that the caller has checked that
 //    aRange and aSubtract do indeed overlap
 
-nsresult Selection::SubtractRange(StyledRange& aRange, nsRange& aSubtract,
-                                  nsTArray<StyledRange>* aOutput) {
+// static
+nsresult Selection::StyledRanges::SubtractRange(
+    StyledRange& aRange, nsRange& aSubtract, nsTArray<StyledRange>* aOutput) {
   nsRange* range = aRange.mRange;
 
   if (NS_WARN_IF(!range->IsPositioned())) {

dom/base/Selection.h

@@ -152,8 +152,6 @@ class Selection final : public nsSupportsWeakReference,
   MOZ_CAN_RUN_SCRIPT nsresult
   ScrollIntoView(SelectionRegion aRegion, ScrollAxis aVertical = ScrollAxis(),
                  ScrollAxis aHorizontal = ScrollAxis(), int32_t aFlags = 0);
-  static nsresult SubtractRange(StyledRange& aRange, nsRange& aSubtract,
-                                nsTArray<StyledRange>* aOutput);
 
  private:
   static bool AreUserSelectedRangesNonEmpty(
@@ -837,6 +835,9 @@ class Selection final : public nsSupportsWeakReference,
 
     void MaybeFocusCommonEditingHost(PresShell* aPresShell) const;
 
+    static nsresult SubtractRange(StyledRange& aRange, nsRange& aSubtract,
+                                  nsTArray<StyledRange>* aOutput);
+
     // These are the ranges inside this selection. They are kept sorted in order
     // of DOM start position.
     //