Fix #2699, use JS to open terms and privacy links on click

This workaround is required because of a bug with e10s handling of https
URLs inside moz-extension pages.

As mentioned in the code comments, this workaround can be removed
once bugzilla bug 1357589 is fixed.

addon/webextension/background/main.js

@@ -272,5 +272,15 @@ this.main = (function() {
     });
   });
 
+  // Note: this signal is only needed until bug 1357589 is fixed.
+  communication.register("openTermsPage", () => {
+    return catcher.watchPromise(browser.tabs.create({url: "https://www.mozilla.org/about/legal/terms/services/"}));
+  });
+
+  // Note: this signal is also only needed until bug 1357589 is fixed.
+  communication.register("openPrivacyPage", () => {
+    return catcher.watchPromise(browser.tabs.create({url: "https://www.mozilla.org/privacy/firefox-cloud/"}));
+  });
+
   return exports;
 })();

addon/webextension/onboarding/slides.js

@@ -107,6 +107,7 @@ this.slides = (function() {
         el.href = linkUrls[part];
         el.textContent = linkTexts[part];
         el.target = "_blank";
+        el.id = (part === termsSentinal) ? "terms" : "privacy";
       } else {
         el = doc.createTextNode(part);
       }
@@ -140,6 +141,16 @@ this.slides = (function() {
       shooter.sendEvent("finish-slides", "done");
       callbacks.onEnd();
     })));
+    // Note: e10s breaks the terms and privacy anchor tags. Work around this by
+    // manually opening the correct URLs on click until bug 1357589 is fixed.
+    doc.querySelector("#terms").addEventListener("click", watchFunction(assertIsTrusted((event) => {
+      event.preventDefault();
+      callBackground("openTermsPage");
+    })));
+    doc.querySelector("#privacy").addEventListener("click", watchFunction(assertIsTrusted((event) => {
+      event.preventDefault();
+      callBackground("openPrivacyPage");
+    })));
     setSlide(1);
   }