Bug 1510785 - Add way to disable XBL in servo. r=emilio

Adds a feature "moz_xbl" that when disabled causes the XBL code in servo to
be stubbed out.

Depends on D45613

Differential Revision: https://phabricator.services.mozilla.com/D45614

--HG--
extra : moz-landing-system : lando

servo/components/style/Cargo.toml

@@ -25,6 +25,7 @@ servo-layout-2020 = []
 gecko_debug = []
 gecko_refcount_logging = []
 gecko_profiler = []
+moz_xbl = []
 
 [dependencies]
 app_units = "0.7"

servo/components/style/gecko/wrapper.rs

@@ -54,8 +54,12 @@ use crate::gecko_bindings::structs::NODE_DESCENDANTS_NEED_FRAMES;
 use crate::gecko_bindings::structs::NODE_NEEDS_FRAME;
 use crate::gecko_bindings::structs::{nsAtom, nsIContent, nsINode_BooleanFlag};
 use crate::gecko_bindings::structs::{
-    nsINode as RawGeckoNode, nsXBLBinding as RawGeckoXBLBinding, Element as RawGeckoElement,
+    nsINode as RawGeckoNode, Element as RawGeckoElement,
 };
+#[cfg(feature = "moz_xbl")]
+use crate::gecko_bindings::structs::nsXBLBinding as RawGeckoXBLBinding;
+#[cfg(not(feature = "moz_xbl"))]
+use values::Impossible;
 use crate::gecko_bindings::sugar::ownership::{HasArcFFI, HasSimpleFFI};
 use crate::global_style_data::GLOBAL_STYLE_DATA;
 use crate::hash::FxHashMap;
@@ -529,9 +533,11 @@ impl<'a> Iterator for GeckoChildrenIterator<'a> {
 }
 
 /// A Simple wrapper over a non-null Gecko `nsXBLBinding` pointer.
+#[cfg(feature = "moz_xbl")]
 #[derive(Clone, Copy)]
 pub struct GeckoXBLBinding<'lb>(pub &'lb RawGeckoXBLBinding);
 
+#[cfg(feature = "moz_xbl")]
 impl<'lb> GeckoXBLBinding<'lb> {
     #[inline]
     fn base_binding(&self) -> Option<Self> {
@@ -556,6 +562,23 @@ impl<'lb> GeckoXBLBinding<'lb> {
     }
 }
 
+/// A stub wraper for GeckoXBLBinding.
+#[cfg(not(feature = "moz_xbl"))]
+pub struct GeckoXBLBinding<'lb>(&'lb Impossible);
+
+#[cfg(not(feature = "moz_xbl"))]
+impl<'lb> GeckoXBLBinding<'lb> {
+
+    #[inline]
+    fn anon_content(&self) -> *const nsIContent {
+        match *self.0 {}
+    }
+
+    fn binding_with_content(&self) -> Option<Self> {
+        None
+    }
+}
+
 /// A simple wrapper over a non-null Gecko `Element` pointer.
 #[derive(Clone, Copy)]
 pub struct GeckoElement<'le>(pub &'le RawGeckoElement);
@@ -681,11 +704,13 @@ impl<'le> GeckoElement<'le> {
         })
     }
 
+    #[cfg(feature = "moz_xbl")]
     #[inline]
     fn may_be_in_binding_manager(&self) -> bool {
         self.flags() & (structs::NODE_MAY_BE_IN_BINDING_MNGR as u32) != 0
     }
 
+    #[cfg(feature = "moz_xbl")]
     #[inline]
     fn xbl_binding(&self) -> Option<GeckoXBLBinding<'le>> {
         if !self.may_be_in_binding_manager() {
@@ -696,6 +721,12 @@ impl<'le> GeckoElement<'le> {
         unsafe { slots.mXBLBinding.mRawPtr.as_ref().map(GeckoXBLBinding) }
     }
 
+    #[cfg(not(feature = "moz_xbl"))]
+    #[inline]
+    fn xbl_binding(&self) -> Option<GeckoXBLBinding<'le>> {
+        None
+    }
+
     #[inline]
     fn xbl_binding_with_content(&self) -> Option<GeckoXBLBinding<'le>> {
         self.xbl_binding().and_then(|b| b.binding_with_content())

servo/ports/geckolib/Cargo.toml

@@ -12,6 +12,7 @@ path = "lib.rs"
 gecko_debug = ["style/gecko_debug", "nsstring/gecko_debug"]
 gecko_profiler = ["style/gecko_profiler"]
 gecko_refcount_logging = ["style/gecko_refcount_logging", "servo_arc/gecko_refcount_logging"]
+moz_xbl = ["style/moz_xbl"]
 
 [dependencies]
 atomic_refcell = "0.1"

toolkit/content/xul.css

@@ -630,3 +630,7 @@ tabmodalprompt {
   [ordinal="9"] { -moz-box-ordinal-group: 9; }
   [ordinal="1000"] { -moz-box-ordinal-group: 1000; }
 }
+
+%ifndef MOZ_XBL
+* { -moz-binding: none !important }
+%endif

toolkit/library/gtest/rust/Cargo.toml

@@ -27,6 +27,7 @@ new_xulstore = ["gkrust-shared/new_xulstore"]
 new_cert_storage = ["gkrust-shared/new_cert_storage"]
 fuzzing_interfaces = ["gkrust-shared/fuzzing_interfaces", "gecko-fuzz-targets"]
 webrtc = ["gkrust-shared/webrtc"]
+moz_xbl = ["gkrust-shared/moz_xbl"]
 
 [dependencies]
 bench-collections-gtest = { path = "../../../../xpcom/rust/gtest/bench-collections" }

toolkit/library/rust/Cargo.toml

@@ -28,6 +28,7 @@ new_xulstore = ["gkrust-shared/new_xulstore"]
 new_cert_storage = ["gkrust-shared/new_cert_storage"]
 fuzzing_interfaces = ["gkrust-shared/fuzzing_interfaces"]
 webrtc = ["gkrust-shared/webrtc"]
+moz_xbl = ["gkrust-shared/moz_xbl"]
 
 [dependencies]
 gkrust-shared = { path = "shared" }

toolkit/library/rust/gkrust-features.mozbuild

@@ -25,6 +25,9 @@ if CONFIG['MOZ_AUDIOUNIT_RUST']:
 if CONFIG['MOZ_RUST_SIMD']:
     gkrust_features += ['simd-accel']
 
+if CONFIG['MOZ_XBL']:
+    gkrust_features += ['moz_xbl']
+
 # This feature is not yet supported on all platforms, and this check needs to
 # match MOZ_CUBEB_REMOTING in CubebUtils.cpp.
 if (CONFIG['OS_ARCH'] == 'Linux' and CONFIG['OS_TARGET'] != 'Android') or CONFIG['OS_ARCH'] == 'Darwin' or (CONFIG['OS_ARCH'] == 'WINNT' and CONFIG['CPU_ARCH'] != 'aarch64'):

toolkit/library/rust/shared/Cargo.toml

@@ -69,6 +69,7 @@ new_xulstore = ["xulstore"]
 new_cert_storage = ["cert_storage"]
 fuzzing_interfaces = []
 webrtc = ["mdns_service"]
+moz_xbl = ["geckoservo/moz_xbl"]
 
 [lib]
 path = "lib.rs"