Bug 1792698 - stop ignoring LOCATION_CHANGE_SAME_DOCUMENT notifications when deciding whether to sync tabs. r=skhamis

Differential Revision: https://phabricator.services.mozilla.com/D161228

services/sync/modules/engines/tabs.js

@@ -522,10 +522,11 @@ TabTracker.prototype = {
 
   // web progress listeners.
   onLocationChange(webProgress, request, locationURI, flags) {
-    // We only care about top-level location changes which are not in the same
-    // document.
+    // We only care about top-level location changes. We do want location changes in the
+    // same document because if a page uses the `pushState()` API, they *appear* as though
+    // they are in the same document even if the URL changes. It also doesn't hurt to accurately
+    // reflect the fragment changing - so we allow LOCATION_CHANGE_SAME_DOCUMENT
     if (
-      flags & Ci.nsIWebProgressListener.LOCATION_CHANGE_SAME_DOCUMENT ||
       flags & Ci.nsIWebProgressListener.LOCATION_CHANGE_RELOAD ||
       !webProgress.isTopLevel ||
       !locationURI
@@ -588,7 +589,14 @@ TabTracker.prototype = {
         "tabsQuickWriteTimer"
       );
     } else if (scoreIncrement) {
+      this._log.debug(
+        "Detected a tab change, but conditions aren't met for a quick write - bumping score"
+      );
       this.score += scoreIncrement;
+    } else {
+      this._log.debug(
+        "Detected a tab change, but conditions aren't met for a quick write or a score bump"
+      );
     }
   },
 };

services/sync/tests/unit/test_tab_tracker.js

@@ -172,8 +172,8 @@ add_task(async function run_test() {
     Ci.nsIWebProgressListener.LOCATION_CHANGE_SAME_DOCUMENT
   );
   Assert.ok(
-    !tracker.modified,
-    "location change within the same document request didn't flag as modified"
+    tracker.modified,
+    "location change within the same document request did flag as modified"
   );
 
   tracker.onLocationChange(