Bug 1838415 - Introduce RFPTarget::RoundWindowSize. r=tjr

Differential Revision: https://phabricator.services.mozilla.com/D181239

toolkit/components/resistfingerprinting/RFPTargets.inc

@@ -67,6 +67,7 @@ ITEM_VALUE(FontVisibilityBaseSystem,    1llu << 42)
 ITEM_VALUE(FontVisibilityLangPack,      1llu << 43)
 ITEM_VALUE(DeviceSensors,               1llu << 44)
 ITEM_VALUE(FrameRate,                   1llu << 45)
+ITEM_VALUE(RoundWindowSize,             1llu << 46)
 
 // !!! Don't forget to update kDefaultFingerintingProtections in nsRFPService.cpp
 // if necessary.

toolkit/components/windowwatcher/nsWindowWatcher.cpp

@@ -2337,7 +2337,7 @@ static void SizeOpenedWindow(nsIDocShellTreeOwner* aTreeOwner,
                 "complicated, and this is a conservative behavior to avoid "
                 "exempting something that shouldn't be. It also presents a "
                 "uniform behavior for something that's very browser-related.",
-                RFPTarget::Unknown)) {
+                RFPTarget::RoundWindowSize)) {
           /* Unlike position, force size out-of-bounds check only if
              size actually was specified. Otherwise, intrinsically sized
              windows are broken. */

xpfe/appshell/AppWindow.cpp

@@ -2700,7 +2700,7 @@ void AppWindow::SizeShell() {
   if (nsContentUtils::ShouldResistFingerprinting(
           "if RFP is enabled we want to round the dimensions of the new"
           "new pop up window regardless of their origin",
-          RFPTarget::Unknown) &&
+          RFPTarget::RoundWindowSize) &&
       windowType.EqualsLiteral("navigator:browser")) {
     // Once we've got primary content, force dimensions.
     if (mPrimaryContentShell || mPrimaryBrowserParent) {