FasterLocationReload: use ReloadMainResource for JS exposed reloads

third_party/WebKit/LayoutTests/http/tests/cache/location-reload.html

+<!DOCYUPE html>
+<script src="../resources/testharness.js"></script>
+<script src="../resources/testharnessreport.js"></script>
+<script>
+
+async_test(t => {
+  let testWindow = null;
+  let messageCount = 0;
+
+  // Test will run on testWindow that is opened below.
+  // This page just received messages to confirm if tests run expectedly.
+  const checkReady = e => {
+    t.step(() => {
+      // Will receive "READY" twice because of a reload, then receive "PASS".
+      assert_equals(e.data, "READY", "received message is " + e.data);
+      messageCount++;
+
+      if (messageCount == 2) {
+        window.removeEventListener("message", checkReady, false);
+        window.addEventListener("message", e => {
+          assert_equals(e.data, "PASS", "received message is " + e.data);
+          t.done();
+        }, { once: true });
+      }
+
+      // Send back "START" message for "READY".
+      assert_class_string(testWindow, "Window", "testWindow is invalid");
+      testWindow.postMessage("START", location.origin);
+    });
+  };
+  window.addEventListener("message", checkReady, false);
+
+  // Start a test in a dedicated window because we can not track navigations
+  // within a test harness.
+  t.step(() => {
+    testWindow = open("./resources/location-reload-window.html", "testWindow");
+    assert_class_string(testWindow, "Window", "window.open() failed");
+  });
+}, "Test location.reload() cache behaviors");
+</script>