[blink][web_tests] document-write tests cleanup

- Add better assertion failure messages
- Use better content for document.write

The tests assume that the ignore-destructive-writes counter is only
incremented during the synchronous part of module evaluation (see
https://github.com/whatwg/html/pull/4352#issuecomment-611193922).

This also fixes document-write/module-delayed.html which accidentally
had wrong test expectations checked in that made it pass.

Bug: 1127215
Bug: 1022182
Bug: v8:9344
Change-Id: I01a75534f7efd0bd8e376dfd049432e52661604d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2397696Reviewed-by: Hiroshige Hayashizaki <hiroshige@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#807384}

third_party/blink/web_tests/external/wpt/html/webappapis/dynamic-markup-insertion/document-write/module-delayed-expected.txt

-This is a testharness.js-based test.
-FAIL async document.write in a module assert_equals: expected "Initial body contents\n" but got "document.write body contents\n"
-Harness: the test ran to completion.
-

third_party/blink/web_tests/external/wpt/html/webappapis/dynamic-markup-insertion/document-write/module-delayed.html

@@ -10,16 +10,17 @@ async_test(t => {
   const iframe = document.createElement("iframe");
 
   iframe.onerror = t.unreached_func("Error loading iframe");
+
   let onLoadWasCalled = false;
   iframe.onload = t.step_func(() => {
+    onLoadWasCalled = true;
     assert_equals(iframe.contentDocument.body.textContent, "Initial body contents\n");
     // Don't call the event handler another time after document.write.
     iframe.onload = null;
-    onLoadWasCalled = true;
   });
   document.addEventListener("documentWriteDone", t.step_func_done(() => {
-    assert_equals(iframe.onload, null);
-    assert_equals(iframe.contentDocument.body.textContent, "Initial body contents\n");
+    assert_true(onLoadWasCalled, "onload must be called");
+    assert_equals(iframe.contentDocument.body.textContent, "document.write body contents\n");
   }));
 
   iframe.src = "module-delayed-iframe.html";

third_party/blink/web_tests/external/wpt/html/webappapis/dynamic-markup-insertion/document-write/module-dynamic-import.html

@@ -8,14 +8,16 @@ async_test(t => {
   const iframe = document.createElement("iframe");
 
   iframe.onerror = t.unreached_func("Error loading iframe");
+
   let onLoadWasCalled = false;
   iframe.onload = t.step_func(() => {
+    onLoadWasCalled = true;
     assert_equals(iframe.contentDocument.body.textContent, "Initial body contents\n");
+    // Don't call the event handler another time after document.write.
     iframe.onload = null;
-    onLoadWasCalled = true;
   });
   document.addEventListener("documentWriteDone", t.step_func_done(() => {
-    assert_true(onLoadWasCalled);
+    assert_true(onLoadWasCalled, "onload must be called");
     assert_equals(iframe.contentDocument.body.textContent, "document.write body contents\n");
   }));
 

third_party/blink/web_tests/external/wpt/html/webappapis/dynamic-markup-insertion/document-write/module-static-import-delayed.html

@@ -8,16 +8,17 @@ async_test(t => {
   // Expose {test} in the iframe for using the step_timeout helper.
   document.test = t;
   const iframe = document.createElement("iframe");
-
   iframe.onerror = t.unreached_func("Error loading iframe");
+
   let onLoadWasCalled = false;
   iframe.onload = t.step_func(() => {
+    onLoadWasCalled = true;
     assert_equals(iframe.contentDocument.body.textContent, "Initial body contents\n");
+    // Don't call the event handler another time after document.write.
     iframe.onload = null;
-    onLoadWasCalled = true;
   });
   document.addEventListener("documentWriteDone", t.step_func_done(() => {
-    assert_true(onLoadWasCalled);
+    assert_true(onLoadWasCalled, "onload must be called");
     assert_equals(iframe.contentDocument.body.textContent, "document.write body contents\n");
   }));
 

third_party/blink/web_tests/external/wpt/html/webappapis/dynamic-markup-insertion/document-write/module-static-import.html

@@ -6,15 +6,16 @@
 <script>
 async_test(t => {
   const iframe = document.createElement("iframe");
+
   iframe.onerror = t.unreached_func("Error loading iframe");
 
   let testEndWasCalled = false;
   document.addEventListener("documentWriteDone", t.step_func(() => {
-    assert_equals(iframe.contentDocument.body.textContent, "Initial body contents\n");
     testEndWasCalled = true;
+    assert_equals(iframe.contentDocument.body.textContent, "Initial body contents\n");
   }));
   iframe.onload = t.step_func_done(() => {
-    assert_true(testEndWasCalled);
+    assert_true(testEndWasCalled, "onload must be called");
     assert_equals(iframe.contentDocument.body.textContent, "Initial body contents\n");
   });
 

third_party/blink/web_tests/external/wpt/html/webappapis/dynamic-markup-insertion/document-write/module-tla-delayed-iframe.html

@@ -4,7 +4,7 @@ let delay = new Promise(
     resolve => window.parent.document.test.step_timeout(resolve, 0));
 
 delay.then(() => {
-  document.write("FAIL");
+  document.write("document.write body contents\n");
   document.close();
   window.parent.document.dispatchEvent(new CustomEvent("documentWriteDone"));
 });

third_party/blink/web_tests/external/wpt/html/webappapis/dynamic-markup-insertion/document-write/module-tla-delayed.html

@@ -15,13 +15,13 @@ async_test(t => {
 
   let onLoadWasCalled = false;
   iframe.onload = t.step_func(() => {
+    onLoadWasCalled = true;
     assert_equals(iframe.contentDocument.body.textContent, "Initial body contents\n");
     iframe.onload = null;
-    onLoadWasCalled = true;
   });
   document.addEventListener("documentWriteDone", t.step_func_done(() => {
-    assert_true(onLoadWasCalled);
-    assert_equals(iframe.contentDocument.body.textContent, "Initial body contents\n");
+    assert_true(onLoadWasCalled, "onload must be called");
+    assert_equals(iframe.contentDocument.body.textContent, "document.write body contents\n");
   }));
 
   iframe.src = "module-tla-delayed-iframe.html";

third_party/blink/web_tests/external/wpt/html/webappapis/dynamic-markup-insertion/document-write/module-tla-immediate-promise.html

@@ -9,16 +9,17 @@ async_test(t => {
   document.test = t;
 
   const iframe = document.createElement("iframe");
-
   iframe.onerror = t.unreached_func("Error loading iframe");
+
   let onLoadWasCalled = false;
   iframe.onload = t.step_func(() => {
+    onLoadWasCalled = true;
     assert_equals(iframe.contentDocument.body.textContent, "Initial body contents\n");
+    // Don't call the event handler another time after document.write.
     iframe.onload = null;
-    onLoadWasCalled = true;
   });
   document.addEventListener("documentWriteDone", t.step_func_done(() => {
-    assert_true(onLoadWasCalled);
+    assert_false(onLoadWasCalled, "onload must not be called yet");
     assert_equals(iframe.contentDocument.body.textContent, "Initial body contents\n");
   }));