Bug 1743310 - Remove paint flahing support from the layout debugger. r=hiro

Doesn't do anything particularly useful nowadays, see above.

Differential Revision: https://phabricator.services.mozilla.com/D132312

layout/tools/layout-debug/ui/content/layoutdebug.js

@@ -23,7 +23,6 @@ const { Preferences } = ChromeUtils.import(
 const { Services } = ChromeUtils.import("resource://gre/modules/Services.jsm");
 
 const FEATURES = {
-  paintFlashing: "nglayout.debug.paint_flashing",
   paintDumping: "nglayout.debug.paint_dumping",
   invalidateDumping: "nglayout.debug.invalidate_dumping",
   eventDumping: "nglayout.debug.event_dumping",
@@ -403,7 +402,6 @@ function checkPersistentMenu(item) {
 
 function checkPersistentMenus() {
   // Restore the toggles that are stored in prefs.
-  checkPersistentMenu("paintFlashing");
   checkPersistentMenu("paintDumping");
   checkPersistentMenu("invalidateDumping");
   checkPersistentMenu("eventDumping");

layout/tools/layout-debug/ui/content/layoutdebug.xhtml

@@ -75,7 +75,6 @@
             <menuitem type="checkbox" id="menu_visualDebugging" label="&ldb.visualDebugging.label;" accesskey="&ldb.visualDebugging.accesskey;" oncommand="toggle(this);" />
             <menuitem type="checkbox" id="menu_visualEventDebugging" label="&ldb.visualEventDebugging.label;" accesskey="&ldb.visualEventDebugging.accesskey;" oncommand="toggle(this);" />
             <menuseparator />
-            <menuitem type="checkbox" id="menu_paintFlashing" label="&ldb.paintFlashing.label;" accesskey="&ldb.paintFlashing.accesskey;" oncommand="toggle(this);" />
             <menuitem type="checkbox" id="menu_paintDumping" label="&ldb.paintDumping.label;" accesskey="&ldb.paintDumping.accesskey;" oncommand="toggle(this);" />
             <menuitem type="checkbox" id="menu_invalidateDumping" label="&ldb.invalidateDumping.label;" accesskey="&ldb.invalidateDumping.accesskey;" oncommand="toggle(this);" />
             <menuseparator />

layout/tools/layout-debug/ui/locale/en-US/layoutdebug.dtd

@@ -19,8 +19,6 @@
 <!ENTITY ldb.visualDebugging.accesskey "V">
 <!ENTITY ldb.visualEventDebugging.label "Visual Event Debugging">
 <!ENTITY ldb.visualEventDebugging.accesskey "E">
-<!ENTITY ldb.paintFlashing.label "Paint Flashing">
-<!ENTITY ldb.paintFlashing.accesskey "F">
 <!ENTITY ldb.paintDumping.label "Paint Dumping">
 <!ENTITY ldb.paintDumping.accesskey "P">
 <!ENTITY ldb.invalidateDumping.label "Invalidate Dumping">