Bug 1820280 - Enable chrome rules in Thunderbird's about:3pane. r=aleca,dholbert

For now a static list of URIs is probably fine. I asked Nika / Gijs if
we can do something better in any case.

We already have tests for stuff not getting exposed to content.

Differential Revision: https://phabricator.services.mozilla.com/D171641

dom/prototype/PrototypeDocumentContentSink.cpp

@@ -8,6 +8,7 @@
 #include "mozilla/dom/PrototypeDocumentContentSink.h"
 #include "nsIParser.h"
 #include "mozilla/dom/Document.h"
+#include "mozilla/dom/URL.h"
 #include "nsIContent.h"
 #include "nsIURI.h"
 #include "nsNetUtil.h"

layout/style/FontFace.h

@@ -17,6 +17,8 @@
 #include "nsWrapperCache.h"
 
 class gfxFontFaceBufferSource;
+class nsIGlobalObject;
+
 struct RawServoFontFaceRule;
 
 namespace mozilla {
@@ -44,8 +46,7 @@ class FontFace final : public nsISupports, public nsWrapperCache {
   NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS(FontFace)
 
   nsIGlobalObject* GetParentObject() const { return mParent; }
-  virtual JSObject* WrapObject(JSContext* aCx,
+  JSObject* WrapObject(JSContext*, JS::Handle<JSObject*> aGivenProto) override;
-                               JS::Handle<JSObject*> aGivenProto) override;
 
   static already_AddRefed<FontFace> CreateForRule(nsIGlobalObject* aGlobal,
                                                   FontFaceSet* aFontFaceSet,

layout/style/URLExtraData.cpp

@@ -9,6 +9,7 @@
 #include "mozilla/URLExtraData.h"
 
 #include "mozilla/NullPrincipal.h"
+#include "nsAboutProtocolUtils.h"
 #include "ReferrerInfo.h"
 
 namespace mozilla {
@@ -29,6 +30,32 @@ void URLExtraData::Init() {
   sDummyChrome->mChromeRulesEnabled = true;
 }
 
+static bool IsPrivilegedAboutURIForCSS(nsIURI* aURI) {
+#ifdef MOZ_THUNDERBIRD
+  if (!aURI->SchemeIs("about")) {
+    return false;
+  }
+  // TODO: we might want to do something a bit less special-casey, perhaps using
+  // nsIAboutModule::GetChromeURI or so? But nsIAboutModule can involve calling
+  // into JS so this is probably fine for now, if it doesn't get too unwieldy.
+  nsAutoCString name;
+  if (NS_WARN_IF(NS_FAILED(NS_GetAboutModuleName(aURI, name)))) {
+    return false;
+  }
+  return name.EqualsLiteral("3pane") || name.EqualsLiteral("addressbook");
+#else
+  return false;
+#endif
+}
+
+bool URLExtraData::ChromeRulesEnabled(nsIURI* aURI) {
+  if (!aURI) {
+    return false;
+  }
+  return aURI->SchemeIs("chrome") || aURI->SchemeIs("resource") ||
+         IsPrivilegedAboutURIForCSS(aURI);
+}
+
 /* static */
 void URLExtraData::Shutdown() {
   sDummy = nullptr;

layout/style/URLExtraData.h

@@ -13,7 +13,6 @@
 
 #include "mozilla/StaticPtr.h"
 #include "mozilla/UserAgentStyleSheetID.h"
-#include "mozilla/dom/URL.h"
 #include "nsCOMPtr.h"
 #include "nsIPrincipal.h"
 #include "nsIReferrerInfo.h"
@@ -22,9 +21,7 @@
 namespace mozilla {
 
 struct URLExtraData {
-  static bool ChromeRulesEnabled(nsIURI* aURI) {
+  static bool ChromeRulesEnabled(nsIURI* aURI);
-    return aURI && (aURI->SchemeIs("chrome") || aURI->SchemeIs("resource"));
-  }
 
   URLExtraData(already_AddRefed<nsIURI> aBaseURI,
                already_AddRefed<nsIReferrerInfo> aReferrerInfo,