Bug 1250966 - Ignore retaining paths that are strictly a super set of other paths. r=jimb

devtools/shared/heapsnapshot/shortest-paths.js

@@ -48,8 +48,20 @@ exports.deduplicatePaths = function (target, paths) {
     nameSet.add(name);
   }
 
-  for (let path of paths) {
+  outer: for (let path of paths) {
     const pathLength = path.length;
+
+    // Check for duplicate predecessors in the path, and skip paths that contain
+    // them.
+    const predecessorsSeen = new Set();
+    predecessorsSeen.add(target);
+    for (let i = 0; i < pathLength; i++) {
+      if (predecessorsSeen.has(path[i].predecessor)) {
+        continue outer;
+      }
+      predecessorsSeen.add(path[i].predecessor);
+    }
+
     for (let i = 0; i < pathLength - 1; i++) {
       insert(path[i].predecessor, path[i + 1].predecessor, path[i].edge);
     }

devtools/shared/heapsnapshot/tests/unit/test_deduplicatePaths_01.js

@@ -104,12 +104,10 @@ function run_test() {
         pathEntry(f, "f->g"),
       ],
     ],
-    expectedNodes: [a, b, f, g],
+    expectedNodes: [a, b, g],
     expectedEdges: [
       edge(a, b, "a->b"),
       edge(b, g, "b->g"),
-      edge(g, f, "g->f"),
-      edge(f, g, "f->g"),
     ]
   });
 }