Adds support for calling postMessage on a frame living in a different renderer.

chrome/test/data/click-noreferrer-links.html

Index: chrome/test/data/click-noreferrer-links.html
diff --git a/chrome/test/data/click-noreferrer-links.html b/chrome/test/data/click-noreferrer-links.html
index 867279ac11be0278cbc08ae3a823bcf5626ee472..f9b1a0d9784da4626eb8c2197e2fa65d5f1b620a 100644
--- a/chrome/test/data/click-noreferrer-links.html
+++ b/chrome/test/data/click-noreferrer-links.html
@@ -24,6 +24,10 @@
     return simulateClick(document.getElementById("samesite_targeted_link"));
   }
 
+  function clickSameSiteTargetBlankLink() {
+    return simulateClick(document.getElementById("samesite_tblank_link"));
+  }
+
   function clickTargetBlankLink() {
     return simulateClick(document.getElementById("tblank_link"));
   }
@@ -46,6 +50,13 @@
     return true;
   }
 
+  // Listen to incoming messages and reply to them.
+  var receivedMessages = 0;
+  window.addEventListener("message", messageReceived, false);
+  function messageReceived(event) {
+    receivedMessages++;
+    event.source.postMessage(event.data, "*");
+  }
  </script>
  </head>
 
@@ -56,6 +67,9 @@
    rel="noreferrer" target="foo">
   same-site rel=noreferrer and target=foo</a><br>
 <a href="navigate_opener.html" id="samesite_targeted_link" target="foo">
+  same-site target=foo</a><br>
+<a href="title2.html" id="samesite_tblank_link" target="_blank">
+  same-site target=_blank</a><br>
 <a href="https://REPLACE_WITH_HOST_AND_PORT/files/title2.html" id="tblank_link"
    target="_blank">target=_blank</a><br>
 <a href="https://REPLACE_WITH_HOST_AND_PORT/files/title2.html" id="noref_link"