XMLHttpRequest::overrideMimeType should throw InvalidStateError

LayoutTests/http/tests/xmlhttprequest/xmlhttprequest-overridemimetype-allowedState-expected.txt

Index: LayoutTests/http/tests/xmlhttprequest/xmlhttprequest-overridemimetype-allowedState-expected.txt
diff --git a/LayoutTests/http/tests/xmlhttprequest/xmlhttprequest-overridemimetype-allowedState-expected.txt b/LayoutTests/http/tests/xmlhttprequest/xmlhttprequest-overridemimetype-allowedState-expected.txt
new file mode 100644
index 0000000000000000000000000000000000000000..39d4d40f371929a252416e57c9f4e6bb6978c659
--- /dev/null
+++ b/LayoutTests/http/tests/xmlhttprequest/xmlhttprequest-overridemimetype-allowedState-expected.txt
@@ -0,0 +1,18 @@
+Testing overrideMimeType when readyState is 0
+PASS xhr.overrideMimeType('text/plain') did not throw exception.
+Testing overrideMimeType when readyState is 1
+PASS xhr.overrideMimeType('text/plain') did not throw exception.
+Testing overrideMimeType when readyState is 1
+PASS xhr.overrideMimeType('text/plain') did not throw exception.
+Testing overrideMimeType when readyState is 1
+PASS xhr.overrideMimeType('text/plain') did not throw exception.
+Testing overrideMimeType when readyState is 2
+PASS xhr.overrideMimeType('text/plain') did not throw exception.
+Testing overrideMimeType when readyState is 3
+PASS xhr.overrideMimeType('text/plain') threw exception InvalidStateError: Failed to execute 'overrideMimeType' on 'XMLHttpRequest': MimeType cannot be overridden when the state is LOADING or DONE..
+Testing overrideMimeType when readyState is 4
+PASS xhr.overrideMimeType('text/plain') threw exception InvalidStateError: Failed to execute 'overrideMimeType' on 'XMLHttpRequest': MimeType cannot be overridden when the state is LOADING or DONE..
+PASS successfullyParsed is true
+
+TEST COMPLETE
+