fixup! Bug 32308: Use direct browser sizing for letterboxing.

Restore our changes after backporting MozBug 1556002.

browser/components/resistfingerprinting/test/browser/browser_dynamical_window_rounding.js

@@ -53,8 +53,8 @@ function checkForDefaultSetting(
   aRealHeight
 ) {
   // We can get the rounded size by subtracting twice the margin.
-  let targetWidth = aRealWidth - 2 * RFPHelper.steppedRange(aRealWidth, true);
-  let targetHeight = aRealHeight - 2 * RFPHelper.steppedRange(aRealHeight);
+  let targetWidth = aRealWidth - 2 * RFPHelper.steppedSize(aRealWidth, true);
+  let targetHeight = aRealHeight - 2 * RFPHelper.steppedSize(aRealHeight);
 
   // This platform-specific code is explained in the large comment below.
   if (getPlatform() != "linux") {

toolkit/components/resistfingerprinting/RFPHelper.sys.mjs

@@ -522,7 +522,7 @@ class _RFPHelper {
   /**
    * Given a width or height, rounds it with the proper stepping.
    */
-  steppedRange(aDimension, aIsWidth = false) {
+  steppedSize(aDimension, aIsWidth = false) {
     let stepping;
     if (aDimension <= 50) {
       return 0;
@@ -607,10 +607,7 @@ class _RFPHelper {
       // If the set is empty, we will round the content with the default
       // stepping size.
       if (!this._letterboxingDimensions.length) {
-        result = {
-          width: this.steppedRange(aWidth, true),
-          height: this.steppedRange(aHeight),
-        };
+        return r(this.steppedSize(aWidth, true), this.steppedSize(aHeight));
       }
 
       let matchingArea = aWidth * aHeight;