Bug 1875199 - Move documentation of two methods in nsHTMLScrollFrame to nsIScrollableFrame. r=layout-reviewers,emilio DONTBUILD

The documentation for GetScrolledRect() and GetLogicalScrollPosition() in
nsHTMLScrollFrame are clearer and up-to-date [1], but they implements the
nsIScrollableFrame's interface. We should move the documentation to
nsIScrollableFrame.

[1] For example, nsXULScrollFrame has been removed in bug 1600542.

Differential Revision: https://phabricator.services.mozilla.com/D198909

layout/generic/nsGfxScrollFrame.h

@@ -208,31 +208,11 @@ class nsHTMLScrollFrame : public nsContainerFrame,
     }
     return mScrollPort.Size();
   }
-  /**
-   * GetScrolledRect is designed to encapsulate deciding which
-   * directions of overflow should be reachable by scrolling and which
-   * should not.  Callers should NOT depend on it having any particular
-   * behavior.
-   *
-   * This should only be called when the scrolled frame has been
-   * reflowed with the scroll port size given in mScrollPort.
-   *
-   * Currently it allows scrolling down and to the right for
-   * nsHTMLScrollFrames with LTR directionality, and allows scrolling down and
-   * to the left for nsHTMLScrollFrames with RTL directionality.
-   */
   nsRect GetScrolledRect() const final;
   nsRect GetScrollPortRect() const final { return mScrollPort; }
   nsPoint GetScrollPosition() const final {
     return mScrollPort.TopLeft() - mScrolledFrame->GetPosition();
   }
-  /**
-   * For LTR frames, the logical scroll position is the offset of the top left
-   * corner of the frame from the top left corner of the scroll port (same as
-   * GetScrollPosition).
-   * For RTL frames, it is the offset of the top right corner of the frame from
-   * the top right corner of the scroll port
-   */
   nsPoint GetLogicalScrollPosition() const final {
     nsPoint pt;
     pt.x = IsPhysicalLTR()

layout/generic/nsIScrollableFrame.h

@@ -146,15 +146,14 @@ class nsIScrollableFrame : public nsIScrollbarMediator {
    * GetScrolledRect is designed to encapsulate deciding which
    * directions of overflow should be reachable by scrolling and which
    * should not.  Callers should NOT depend on it having any particular
-   * behavior (although nsXULScrollFrame currently does).
+   * behavior.
    *
    * This should only be called when the scrolled frame has been
    * reflowed with the scroll port size given in mScrollPort.
    *
    * Currently it allows scrolling down and to the right for
-   * nsHTMLScrollFrames with LTR directionality and for all
+   * nsHTMLScrollFrames with LTR directionality, and allows scrolling down and
-   * nsXULScrollFrames, and allows scrolling down and to the left for
+   * to the left for nsHTMLScrollFrames with RTL directionality.
-   * nsHTMLScrollFrames with RTL directionality.
    */
   virtual nsRect GetScrolledRect() const = 0;
   /**
@@ -170,7 +169,11 @@ class nsIScrollableFrame : public nsIScrollbarMediator {
    */
   virtual nsPoint GetScrollPosition() const = 0;
   /**
-   * As GetScrollPosition(), but uses the top-right as origin for RTL frames.
+   * For LTR frames, the logical scroll position is the offset of the top left
+   * corner of the frame from the top left corner of the scroll port (same as
+   * GetScrollPosition).
+   * For RTL frames, it is the offset of the top right corner of the frame from
+   * the top right corner of the scroll port.
    */
   virtual nsPoint GetLogicalScrollPosition() const = 0;