[webcrypto] Match the error handling defined by the spec.

LayoutTests/crypto/digest.html

Index: LayoutTests/crypto/digest.html
diff --git a/LayoutTests/crypto/digest.html b/LayoutTests/crypto/digest.html
index cb5255cb0cf01d37f25b36b67a60290127bedf7f..affc8c87f0cd9518bebca26fb74a0393b84ed9fa 100644
--- a/LayoutTests/crypto/digest.html
+++ b/LayoutTests/crypto/digest.html
@@ -98,11 +98,9 @@ kDigestTestVectors = [
   },
 ];
 
-var allTests = [];
-
 // Run each test.
 for (var i = 0; i < kDigestTestVectors.length; ++i) {
-    allTests.push(runTestCase(kDigestTestVectors[i]));
+    addTask(runTestCase(kDigestTestVectors[i]));
 }
 
 function runTestCase(testCase)
@@ -113,9 +111,7 @@ function runTestCase(testCase)
     });
 }
 
-Promise.all(allTests).then(finishJSTest, failAndFinishJSTest);
-
-// Pass invalid data to digeset()
+// Pass invalid data to digest()
 shouldThrow("crypto.subtle.digest({name: 'sha-1'})");
 shouldThrow("crypto.subtle.digest({name: 'sha-1'}, null)");
 shouldThrow("crypto.subtle.digest({name: 'sha-1'}, 10)");
@@ -126,6 +122,8 @@ shouldThrow("crypto.subtle.digest({name: 'sha'}, data)");
 shouldThrow("crypto.subtle.digest(null, data)");
 shouldThrow("crypto.subtle.digest({}, data)");
 
+completeTestWhenAllTasksDone();
+
 </script>
 
 </body>