From 13c49606a497673d830c1a1cac33481574b1d173 Mon Sep 17 00:00:00 2001
From: Cameron McCormack <cam@mcc.id.au>
Date: Tue, 28 Mar 2017 15:32:35 +0800
Subject: [PATCH] stylo: Add argument to Servo_ResolveStyle to allow stale
 styles to be returned.

---
 components/style/gecko_bindings/bindings.rs |  3 ++-
 ports/geckolib/glue.rs                      | 13 ++++++++++---
 2 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/components/style/gecko_bindings/bindings.rs b/components/style/gecko_bindings/bindings.rs
index dd5196defa6..cc79d32bcf4 100644
--- a/components/style/gecko_bindings/bindings.rs
+++ b/components/style/gecko_bindings/bindings.rs
@@ -1812,7 +1812,8 @@ extern "C" {
 }
 extern "C" {
     pub fn Servo_ResolveStyle(element: RawGeckoElementBorrowed,
-                              set: RawServoStyleSetBorrowed)
+                              set: RawServoStyleSetBorrowed,
+                              allow_stale: bool)
      -> ServoComputedValuesStrong;
 }
 extern "C" {
diff --git a/ports/geckolib/glue.rs b/ports/geckolib/glue.rs
index 3ac1fdb8690..6b9c7288481 100644
--- a/ports/geckolib/glue.rs
+++ b/ports/geckolib/glue.rs
@@ -1473,15 +1473,22 @@ pub extern "C" fn Servo_TakeChangeHint(element: RawGeckoElementBorrowed) -> nsCh
 
 #[no_mangle]
 pub extern "C" fn Servo_ResolveStyle(element: RawGeckoElementBorrowed,
-                                     raw_data: RawServoStyleSetBorrowed)
+                                     raw_data: RawServoStyleSetBorrowed,
+                                     allow_stale: bool)
                                      -> ServoComputedValuesStrong
 {
     let element = GeckoElement(element);
     debug!("Servo_ResolveStyle: {:?}", element);
     let data = unsafe { element.ensure_data() }.borrow_mut();
 
-    if !data.has_current_styles() {
-        warn!("Resolving style on unstyled element with lazy computation forbidden.");
+    let valid_styles = if allow_stale {
+      data.has_styles()
+    } else {
+      data.has_current_styles()
+    };
+
+    if !valid_styles {
+        warn!("Resolving style on element without current styles with lazy computation forbidden.");
         let per_doc_data = PerDocumentStyleData::from_ffi(raw_data).borrow();
         return per_doc_data.default_computed_values().clone().into_strong();
     }