Disallow users modify canvas after it transfers control to offscreen

third_party/WebKit/LayoutTests/fast/canvas/OffscreenCanvas-transferControlToOffscreen.html

Index: third_party/WebKit/LayoutTests/fast/canvas/OffscreenCanvas-transferControlToOffscreen.html
diff --git a/third_party/WebKit/LayoutTests/fast/canvas/OffscreenCanvas-transferControlToOffscreen.html b/third_party/WebKit/LayoutTests/fast/canvas/OffscreenCanvas-transferControlToOffscreen.html
index e881b63c0d1e52d926029c1165e6cee65f3e4559..e541808549b9485387e0a383c4e305a6bc0debf4 100644
--- a/third_party/WebKit/LayoutTests/fast/canvas/OffscreenCanvas-transferControlToOffscreen.html
+++ b/third_party/WebKit/LayoutTests/fast/canvas/OffscreenCanvas-transferControlToOffscreen.html
@@ -46,6 +46,26 @@ test(function() {
     assert_throws("InvalidStateError", function() { offscreenCanvas3.height = 20; });
 }, "Test if resizing on offscreencanvas transferred from html canvas has thrown exceptions.");
 
+test(function() {
+    var canvas4 = createCanvas(10, 10);
+    var offscreenCanvas4 = canvas4.transferControlToOffscreen();
+    assert_throws("InvalidStateError", function() {
+        canvas4.getContext("2d");
+    }, "canvas.getContext() is not allowed after transferring control to offscreen.");
+    assert_throws("InvalidStateError", function() {
+        canvas4.height = 20;
+    }, "canvas resizing height is not allowed after transferring control to offscreen.");
+    assert_throws("InvalidStateError", function() {
+        canvas4.width = 20;
+    }, "canvas resizing width is not allowed after transferring control to offscreen.");
+    assert_throws("InvalidStateError", function() {
+        canvas4.toBlob(function() {});
+    }, "canvas.toBlob is not allowed after transferring control to offscreen.");
+    assert_throws("InvalidStateError", function() {
+        canvas4.toDataURL();
+    }, "canvas.toDataURL is not allowed after transferring control to offscreen.");
+}, "Test if modifying canvas after it transfers controls to offscreen throw exceptions");
+
 </script>
 </body>
 </html>