Rework EventSource tests for better Worker test coverage.

LayoutTests/http/tests/eventsource/script-tests/eventsource-content-type-charset.js

+if (self.importScripts)
+    importScripts("/js-test-resources/js-test.js");
+
+description("Test EventSource with an event-stream with a Content-Type with a charset is still recognized.");
+// Test for bug https://bugs.webkit.org/show_bug.cgi?id=45372
+
+self.jsTestIsAsync = true;
+
+var es;
+
+function shouldGetMessage() {
+    debug("Content type: " + es.contentType);
+    shouldBeFalse("!!es.sawError");
+    shouldBeTrue("es.sawMessage");
+    shouldBeTrue("es.sawOpen");
+}
+
+function shouldFail() {
+    debug("Content type: " + es.contentType);
+    shouldBeTrue("es.sawError");
+    shouldBeFalse("!!es.sawMessage");
+    shouldBeFalse("!!es.sawOpen");
+}
+
+var i = 0;
+var contentTypes = [ 'text/event-stream; charset=UTF-8',
+                     'text/event-stream; charset=windows-1251',
+                     'text/event-stream; charset=utf-8',
+                     'text/event-stream; charset="UTF-8"',
+                     'text/event-stream-foobar;'
+                   ];
+
+var expectedResultCallback = [ shouldGetMessage,
+                               shouldFail,
+                               shouldGetMessage,
+                               shouldGetMessage,
+                               shouldFail
+                             ];
+
+function openListener(evt)
+{
+    evt.target.sawOpen = true;
+}
+
+function messageListener(evt)
+{
+    evt.target.sawMessage = true;
+    evt.target.successCallback(evt.target);
+    evt.target.close();
+    next();
+}
+
+function errorListener(evt)
+{
+    evt.target.sawError = true;
+    evt.target.successCallback(evt.target);
+    evt.target.close();
+    next();
+}
+
+function startRequest()
+{
+    shouldNotThrow("es = new EventSource(\"/eventsource/resources/response-content-type-charset.php?contentType=" + escape(contentTypes[i]) + "\")");
+    es.onopen = openListener;
+    es.onmessage = messageListener;
+    es.onerror = errorListener;
+    es.successCallback = expectedResultCallback[i];
+    es.contentType = contentTypes[i];
+    ++i;
+}
+
+function next()
+{
+    if (i >= contentTypes.length) {
+        finishJSTest();
+        return;
+    }
+    startRequest();
+}
+startRequest();