servo · bors-servo · Jun 13, 2017 · Jun 12, 2017 · emilio · Jun 12, 2017
diff --git a/components/canvas/canvas_paint_thread.rs b/components/canvas/canvas_paint_thread.rs
@@ -547,6 +547,10 @@ impl<'a> CanvasPaintThread<'a> {
 
     fn recreate(&mut self, size: Size2D<i32>) {
         self.drawtarget = CanvasPaintThread::create(size);
+        // Webrender doesn't let images change size, so we clear the webrender image key.
+        if let Some(image_key) = self.image_key.take() {
+            self.webrender_api.delete_image(image_key);
+        }
     }
 
     fn send_pixels(&mut self, chan: IpcSender<Option<Vec<u8>>>) {

diff --git a/components/canvas/webgl_paint_thread.rs b/components/canvas/webgl_paint_thread.rs
@@ -291,14 +291,18 @@ impl WebGLPaintThread {
     #[allow(unsafe_code)]
     fn recreate(&mut self, size: Size2D<i32>) -> Result<(), &'static str> {
         match self.data {
-            WebGLPaintTaskData::Readback(ref mut context, _, _) => {
+            WebGLPaintTaskData::Readback(ref mut context, ref webrender_api, ref mut image_key) => {
                 if size.width > self.size.width ||
                    size.height > self.size.height {
                     self.size = try!(context.resize(size));
                 } else {
                     self.size = size;
                     context.gl().scissor(0, 0, size.width, size.height);
                 }
+                // Webrender doesn't let images change size, so we clear the webrender image key.
+                if let Some(image_key) = image_key.take() {
+                    webrender_api.delete_image(image_key);
+                }
             }
             WebGLPaintTaskData::WebRender(ref api, id) => {
                 let device_size = webrender_traits::DeviceIntSize::from_untyped(&size);

diff --git a/tests/wpt/mozilla/meta/MANIFEST.json b/tests/wpt/mozilla/meta/MANIFEST.json
@@ -6449,6 +6449,18 @@
      {}
     ]
    ],
+   "mozilla/canvas/set_dimensions.html": [
+    [
+     "/_mozilla/mozilla/canvas/set_dimensions.html",
+     [
+      [
+       "/_mozilla/mozilla/canvas/set_dimensions_ref.html",
+       "=="
+      ]
+     ],
+     {}
+    ]
+   ],
    "mozilla/details_ui_closed.html": [
     [
      "/_mozilla/mozilla/details_ui_closed.html",
@@ -9570,6 +9582,11 @@
      {}
     ]
    ],
+   "mozilla/canvas/set_dimensions_ref.html": [
+    [
+     {}
+    ]
+   ],
    "mozilla/click_prevent.html": [
     [
      {}

    "794dd75566d0e2086deb0dcfc727dfe1834ca17e",
    "testharness"
   ],
+  "mozilla/canvas/set_dimensions.html": [
+   "db6e4fa9b3480609a9a3a582430c64fb49b2b047",
+   "reftest"
+  ],
+  "mozilla/canvas/set_dimensions_ref.html": [
+   "dd9ab8e1a360063d40e5155c1228e69154fa0966",
+   "support"
+  ],
   "mozilla/caption.html": [
    "51ed2927d2f3910fb9c2dc4bb1ea4d41c261c8c1",
    "testharness"
diff --git a/tests/wpt/mozilla/tests/mozilla/canvas/set_dimensions.html b/tests/wpt/mozilla/tests/mozilla/canvas/set_dimensions.html
@@ -0,0 +1,25 @@
+<!doctype html>
+<html class="reftest-wait">
+    <head>
+        <meta charset=utf-8>
+        <title>Resizing a canvas</title>
+        <link rel=match href=/_mozilla/mozilla/canvas/set_dimensions_ref.html>
+    </head>
+
+    <body>
+        <canvas width="50px" height="50px"></canvas>
+        <script>
+            var canvas = document.getElementsByTagName('canvas')[0];
+            var ctx = canvas.getContext('2d');
+            ctx.fillStyle = "red";
+            ctx.fillRect(0, 0, canvas.width, canvas.height);
+            setTimeout(function() {
+                canvas.width = 100;
+                canvas.height = 100;
+                ctx.fillStyle = "green";
+                ctx.fillRect(0, 0, canvas.width, canvas.height);
+                document.documentElement.classList.remove("reftest-wait");
+            }, 0);
+        </script>
+    </body>
+</html>
diff --git a/tests/wpt/mozilla/tests/mozilla/canvas/set_dimensions_ref.html b/tests/wpt/mozilla/tests/mozilla/canvas/set_dimensions_ref.html
@@ -0,0 +1,17 @@
+<!doctype html>
+<html>
+    <head>
+        <meta charset=utf-8>
+        <title>Resizing a canvas reference</title>
+    </head>
+
+    <body>
+        <canvas width="100px" height="100px"></canvas>
+        <script>
+            var canvas = document.getElementsByTagName('canvas')[0];
+            var ctx = canvas.getContext('2d');
+            ctx.fillStyle = "green";
+            ctx.fillRect(0, 0, canvas.width, canvas.height);
+        </script>
+    </body>
+</html>