Bug 1410360 - reselect original tab after closing about:devtools;r=ochameau

MozReview-Commit-ID: 3bInaF7Zeg9

--HG--
extra : rebase_source : d31509b2264a82d091cfdeacf8e889635f4a65b8

devtools/shim/aboutdevtools/aboutdevtools.js

@@ -21,6 +21,7 @@ const MESSAGES = {
 // we have to use http in order to have working searchParams.
 let url = new URL(window.location.href.replace("about:", "http://"));
 let reason = url.searchParams.get("reason");
+let tabid = parseInt(url.searchParams.get("tabid"), 10);
 
 function getToolboxShortcut() {
   const bundleUrl = "chrome://devtools-shim/locale/key-shortcuts.properties";
@@ -75,6 +76,25 @@ window.addEventListener("load", function () {
   updatePage();
 }, { once: true });
 
+window.addEventListener("beforeunload", function () {
+  // Focus the tab that triggered the DevTools onboarding.
+  if (document.visibilityState != "visible") {
+    // Only try to focus the correct tab if the current tab is the about:devtools page.
+    return;
+  }
+
+  // Retrieve the original tab if it is still available.
+  let browserWindow = Services.wm.getMostRecentWindow("navigator:browser");
+  let { gBrowser } = browserWindow;
+  let originalBrowser = gBrowser.getBrowserForOuterWindowID(tabid);
+  let originalTab = gBrowser.getTabForBrowser(originalBrowser);
+
+  if (originalTab) {
+    // If the original tab was found, select it.
+    gBrowser.selectedTab = originalTab;
+  }
+}, {once: true});
+
 window.addEventListener("unload", function () {
   let installButton = document.getElementById("install");
   installButton.removeEventListener("click", onInstallButtonClick);

devtools/shim/devtools-startup.js

@@ -545,8 +545,19 @@ DevToolsStartup.prototype = {
     }
 
     let url = "about:devtools";
+
+    let params = [];
     if (reason) {
-      url += "?reason=" + encodeURIComponent(reason);
+      params.push("reason=" + encodeURIComponent(reason));
+    }
+
+    let selectedBrowser = gBrowser.selectedBrowser;
+    if (selectedBrowser) {
+      params.push("tabid=" + selectedBrowser.outerWindowID);
+    }
+
+    if (params.length > 0) {
+      url += "?" + params.join("&");
     }
 
     // Set relatedToCurrent: true to open the tab next to the current one.