fix: stop async scripts running between parser pumps

Some pages assume that async scripts don't run in between sync
<script> tags. They probably shouldn't, but this fixes the
behaviour.

Bug: 1197376, 901056
Change-Id: Icd1779f164db77794e25dbcd6e3e92582a55d7a7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2826128
Commit-Queue: Richard Townsend <richard.townsend@arm.com>
Reviewed-by: Kouhei Ueno <kouhei@chromium.org>
Reviewed-by: Mason Freed <masonf@chromium.org>
Cr-Commit-Position: refs/heads/master@{#878839}

html/semantics/scripting-1/the-script-element/async_005.htm

@@ -17,7 +17,10 @@
 
         function timeout()
         {
-            t.step(function(){ assert_equals(document.getElementById("testresult").innerHTML, "2134")});
+            t.step(function(){
+                var actual = document.getElementById("testresult").innerHTML;
+                assert_in_array(actual, ["2134", "2341"]);
+            });
             t.done();
         }
 

html/semantics/scripting-1/the-script-element/execution-timing/050.html

@@ -21,8 +21,28 @@
         var t = async_test()
 
         function test() {
-                assert_array_equals(eventOrder, ['inline script #1', 'end script #1', 'include-5 before removing scripts', 'include-5 after removing scripts', 'external script #1', 'external script #2']),
-                t.done();
+            // Per-spec, non-blocking/async scripts can execute at any time.
+            // Therefore, there are two possibilities for the script order here.
+            // 1. inline script first, followed by include-5 (async), then
+            //    external script #1 (slow async) and finally external #2
+            //    (inline).
+            // 2. inline script, external '2, 'include 5', then include-1.
+            assert_array_equals(eventOrder.slice(0, 2), [
+                'inline script #1', 'end script #1'
+            ]);
+            if (eventOrder[2] == 'include-5 before removing scripts') {
+                assert_array_equals(eventOrder.slice(3), [
+                    'include-5 after removing scripts', 'external script #1',
+                    'external script #2'
+                ]);
+            } else {
+                assert_array_equals(eventOrder.slice(2), ['external script #2',
+                    'include-5 before removing scripts',
+                    'include-5 after removing scripts',
+                    'external script #1'
+                ]);
+            }
+            t.done();
         }
         onload = t.step_func(test)
         </script>