Fix AbortSignal conversion regression

By working around a bug in the IDL compiler when generating RequestInit
with said compiler, a regression was introduced that stopped TypeErrors
from being thrown when RequestInit's signal member does not implement
the AbortSignal interface. This CL fixes that regression and adds tests
for it.

R=kinuko@chromium.org, yoav@yoav.ws

Bug: 836873
Change-Id: I6ab7be2ee8356eb7a997b904d121a7061986096a
Reviewed-on: https://chromium-review.googlesource.com/1123771Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Reviewed-by: Adam Rice <ricea@chromium.org>
Commit-Queue: Dominic Farolino <domfarolino@gmail.com>
Cr-Commit-Position: refs/heads/master@{#572449}

third_party/WebKit/LayoutTests/http/tests/fetch/script-tests/request.js

@@ -677,8 +677,9 @@ test(() => {
   }, 'Used => clone');
 
 test(() => {
-  // We implement RequestInit manually so we need to test the functionality
-  // here.
+  // We used to implement RequestInit manually so we needed to test this
+  // functionality here. We now generate RequestInit with the IDL compiler,
+  // but it's still good to keep these around.
   function undefined_notpresent(property_name) {
     assert_not_equals(property_name, 'referrer', 'property_name');
     const request = new Request('/', {referrer: '/'});
@@ -709,8 +710,9 @@ test(() => {
 }, 'An undefined member should be treated as not-present');
 
 test(() => {
-  // We implement RequestInit manually so we need to test the functionality
-  // here.
+  // We used to implement RequestInit manually so we needed to test this
+  // functionality here. We now generate RequestInit with the IDL compiler,
+  // but it's still good to keep these around.
   const e = Error();
   assert_throws(e, () => {
     new Request('/', {get method() { throw e; }})}, 'method');
@@ -742,6 +744,21 @@ test(() => {
   //  new Request('/', {get window() { throw e; }})}, 'window');
 }, 'Getter exceptions should not be silently ignored');
 
+
+test(() => {
+  // At the time of writing this test, an `any` type is used to represent
+  // RequestInit's signal member instead of AbortSignal due to a bug in the IDL
+  // compiler; see https://crbug.com/855968. This test ensures that that we
+  // treat the `any` member exactly as an AbortSignal member would be treated.
+  const e = TypeError();
+  assert_throws(e, () => {
+    new Request('/', {signal: {}})}, 'signal');
+  assert_throws(e, () => {
+    new Request('/', {signal: new Request('/')})}, 'signal');
+  assert_throws(e, () => {
+    new Request('/', {signal: new Response('/')})}, 'signal');
+}, 'TypeError should be thrown when RequestInit\'s signal member does not implement the AbortSignal interface');
+
 promise_test(function() {
     var headers = new Headers;
     headers.set('Content-Language', 'ja');

third_party/blink/renderer/core/fetch/request.cc

@@ -454,8 +454,17 @@ Request* Request::CreateRequestWithRequestOrString(
   v8::Local<v8::Value> init_signal =
       init.hasSignal() ? init.signal().V8Value() : v8::Local<v8::Value>();
   if (!init_signal.IsEmpty()) {
-    signal = V8AbortSignal::ToImplWithTypeCheck(script_state->GetIsolate(),
-                                                init_signal);
+    if (init_signal->IsNull()) {
+      // This allows a null AbortSignal to override |input_request|'s, which
+      // would otherwise be used.
+      signal = nullptr;
+    } else {
+      signal = NativeValueTraits<AbortSignal>::NativeValue(
+          script_state->GetIsolate(), init_signal, exception_state);
+      if (exception_state.HadException()) {
+        return nullptr;
+      }
+    }
   }
 
   // "Let |r| be a new Request object associated with |request| and a new