Bug 1321754 - Add an enum value to SheetParsingMode for agent sheets …

…that use no unsafe rules. r=heycam

scrollbars.css is the only sheet which is parsed as author level, but later
added as agent level in [1]. Add a new enum value so that it can be parsed
as author level in gecko (nsCSSParser::AgentRulesEnabled() will exclude it),
but servo can recognize it as agent level sheet when the sheet is created.

Delete UserRulesEnabled() because no one uses it.

[1] http://searchfox.org/mozilla-central/rev/7419b368156a6efa24777b21b0e5706be89a9c2f/layout/base/nsDocumentViewer.cpp#2326

MozReview-Commit-ID: 2lrV4ogfnHM

--HG--
extra : rebase_source : 9d80a146f2ec5629999076ea1587e7d36f06afe7

layout/style/SheetParsingMode.h

@@ -24,17 +24,27 @@ namespace css {
  * exposure on the public Web, but are very useful for expressing
  * user style overrides, such as @-moz-document rules.
  *
+ * XXX: eUserSheetFeatures was added in bug 1035091, but some patches in
+ * that bug never landed to use this enum value. Currently, all the features
+ * in user sheet are also available in author sheet.
+ *
  * Agent sheets have access to all author- and user-sheet features
  * plus more extensions that are necessary for internal use but,
  * again, not yet suitable for exposure on the public Web.  Some of
  * these are outright unsafe to expose; in particular, incorrect
  * styling of anonymous box pseudo-elements can violate layout
  * invariants.
+ *
+ * Agent sheets that do not use any unsafe rules could use
+ * eSafeAgentSheetFeatures when creating the sheet. This enum value allows
+ * Servo backend to recognize the sheets as the agent level, but Gecko
+ * backend will parse it under _author_ level.
  */
 enum SheetParsingMode {
   eAuthorSheetFeatures = 0,
   eUserSheetFeatures,
-  eAgentSheetFeatures
+  eAgentSheetFeatures,
+  eSafeAgentSheetFeatures,
 };
 
 } // namespace css

layout/style/nsCSSParser.cpp

@@ -363,10 +363,6 @@ class CSSParserImpl {
   bool ChromeRulesEnabled() const {
     return mIsChrome;
   }
-  bool UserRulesEnabled() const {
-    return mParsingMode == css::eAgentSheetFeatures ||
-           mParsingMode == css::eUserSheetFeatures;
-  }
 
   CSSEnabledState EnabledState() const {
     static_assert(int(CSSEnabledState::eForAllContent) == 0,
@@ -376,7 +372,7 @@ class CSSParserImpl {
     if (AgentRulesEnabled()) {
       enabledState |= CSSEnabledState::eInUASheets;
     }
-    if (mIsChrome) {
+    if (ChromeRulesEnabled()) {
       enabledState |= CSSEnabledState::eInChrome;
     }
     return enabledState;

layout/style/nsLayoutStylesheetCache.cpp

@@ -79,7 +79,7 @@ nsLayoutStylesheetCache::ScrollbarsSheet()
   if (!mScrollbarsSheet) {
     // Scrollbars don't need access to unsafe rules
     LoadSheetURL("chrome://global/skin/scrollbars.css",
-                 &mScrollbarsSheet, eAuthorSheetFeatures, eCrash);
+                 &mScrollbarsSheet, eSafeAgentSheetFeatures, eCrash);
   }
 
   return mScrollbarsSheet;

servo/ports/geckolib/glue.rs

@@ -327,6 +327,7 @@ pub extern "C" fn Servo_StyleSheet_Empty(mode: SheetParsingMode) -> RawServoStyl
         SheetParsingMode::eAuthorSheetFeatures => Origin::Author,
         SheetParsingMode::eUserSheetFeatures => Origin::User,
         SheetParsingMode::eAgentSheetFeatures => Origin::UserAgent,
+        SheetParsingMode::eSafeAgentSheetFeatures => Origin::UserAgent,
     };
     let shared_lock = global_style_data.shared_lock.clone();
     Arc::new(Stylesheet::from_str(
@@ -349,6 +350,7 @@ pub extern "C" fn Servo_StyleSheet_FromUTF8Bytes(loader: *mut Loader,
         SheetParsingMode::eAuthorSheetFeatures => Origin::Author,
         SheetParsingMode::eUserSheetFeatures => Origin::User,
         SheetParsingMode::eAgentSheetFeatures => Origin::UserAgent,
+        SheetParsingMode::eSafeAgentSheetFeatures => Origin::UserAgent,
     };
 
     let url_data = unsafe { RefPtr::from_ptr_ref(&extra_data) };