feat: Mark stylesheets as changed when updating mods, b=no-bug, c=mods

src/layout/base/nsStyleSheetService-h.patch

@@ -0,0 +1,13 @@
+diff --git a/layout/base/nsStyleSheetService.h b/layout/base/nsStyleSheetService.h
+index 8c49b338bf8e6830874ace9a08e8c0713167ee58..115bf09314970fd2fe79793e9cf8e0c40eb0459b 100644
+--- a/layout/base/nsStyleSheetService.h
++++ b/layout/base/nsStyleSheetService.h
+@@ -50,6 +50,8 @@ class nsStyleSheetService final : public nsIStyleSheetService,
+ 
+   size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const;
+ 
++  void ZenMarkStylesAsChanged();
++
+   static nsStyleSheetService* GetInstance();
+   static nsStyleSheetService* gInstance;
+ 

src/zen/mods/ZenMods.mjs

@@ -42,10 +42,8 @@
       await this.#rebuildModsStylesheet();
     }
 
-    #getStylesheetURIForMod(mod) {
-      return Services.io.newFileURI(
-        new FileUtils.File(PathUtils.join(this.getModFolder(mod.id), 'chrome.css'))
-      );
+    #getStylesheetPathForMod(mod) {
+      return PathUtils.join(this.getModFolder(mod.id), 'chrome.css');
     }
 
     async #readStylesheet() {
@@ -223,7 +221,7 @@
       const mods = [];
 
       for (let mod of modList) {
-        mod._chromeURL = this.#getStylesheetURIForMod(mod).spec;
+        mod._filePath = this.#getStylesheetPathForMod(mod);
         mods.push(mod);
       }
 
@@ -244,7 +242,8 @@
           content += `/* Readme: ${mod.readme} */\n`;
         }
 
-        content += `@import url("${mod._chromeURL}");\n`;
+        const chromeContent = await IOUtils.readUTF8(mod._filePath);
+        content += chromeContent;
       }
 
       content += this.#kZenStylesheetModFooter;

src/zen/mods/ZenStyleSheetCache.cpp

@@ -8,6 +8,8 @@
 #include "nsCOMPtr.h"
 #include "nsIFile.h"
 
+#include "nsStyleSheetService.h"
+
 #include "mozilla/css/SheetParsingMode.h"
 #include "mozilla/GlobalStyleSheetCache.h"
 
@@ -82,6 +84,9 @@ nsresult ZenStyleSheetCache::RebuildModsStylesheets(const nsACString& aContents)
   }
   ErrorResult aRv;
   sheet->ReparseSheet(aContents, aRv);
+  if (auto sss = nsStyleSheetService::GetInstance()) {
+    sss->ZenMarkStylesAsChanged();
+  }
   return aRv.StealNSResult();
 }
 

src/zen/mods/nsZenModsBackend.cpp

@@ -51,3 +51,14 @@ auto nsZenModsBackend::RebuildModsStyles(const nsACString& aContents) -> nsresul
 }
 
 } // namespace: zen
+
+auto nsStyleSheetService::ZenMarkStylesAsChanged() -> void {
+  for (auto& presShell : mPresShells) {
+    if (presShell) {
+      if (auto doc = presShell->GetDocument(); doc && doc->IsInChromeDocShell()) {
+        // Notify the document that styles have changed.
+        doc->ApplicableStylesChanged();
+      }
+    }
+  }
+}