CanvasGradient#addColorStop should throw for invalid colors and offsets

components/script/dom/canvasgradient.rs

@@ -2,11 +2,12 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-use cssparser::RGBA;
 use canvas_traits::{CanvasGradientStop, FillOrStrokeStyle, LinearGradientStyle, RadialGradientStyle};
 use dom::bindings::cell::DOMRefCell;
 use dom::bindings::codegen::Bindings::CanvasGradientBinding;
 use dom::bindings::codegen::Bindings::CanvasGradientBinding::CanvasGradientMethods;
+use dom::bindings::error::Error::{IndexSize, Syntax};
+use dom::bindings::error::ErrorResult;
 use dom::bindings::global::GlobalRef;
 use dom::bindings::js::Root;
 use dom::bindings::num::Finite;
@@ -44,18 +45,21 @@ impl CanvasGradient {
 
 impl<'a> CanvasGradientMethods for &'a CanvasGradient {
     // https://html.spec.whatwg.org/multipage/#dom-canvasgradient-addcolorstop
-    fn AddColorStop(self, offset: Finite<f64>, color: String) {
-        let default_black = RGBA {
-            red: 0.0,
-            green: 0.0,
-            blue: 0.0,
-            alpha: 1.0,
+    fn AddColorStop(self, offset: Finite<f64>, color: String) -> ErrorResult {
+        if *offset < 0f64 || *offset > 1f64 {
+            return Err(IndexSize);
+        }
+
+        let color = match parse_color(&color) {
+            Ok(color) => color,
+            _ => return Err(Syntax)
         };
 
         self.stops.borrow_mut().push(CanvasGradientStop {
             offset: (*offset) as f64,
-            color: parse_color(&color).unwrap_or(default_black),
+            color: color,
         });
+        Ok(())
     }
 }
 

components/script/dom/webidls/CanvasGradient.webidl

@@ -7,6 +7,7 @@
 // [Exposed=(Window,Worker)]
 interface CanvasGradient {
   // opaque object
+  [Throws]
   void addColorStop(double offset, DOMString color);
 };