1 files changed, 139 insertions, 0 deletions
diff --git a/devtools/client/memory/test/browser/browser_memory_refresh_does_not_leak.js b/devtools/client/memory/test/browser/browser_memory_refresh_does_not_leak.js
new file mode 100644
index 0000000000..e0ee1eee41
--- /dev/null
+++ b/devtools/client/memory/test/browser/browser_memory_refresh_does_not_leak.js
@@ -0,0 +1,139 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/* global ChromeUtils */
+
+// Test that refreshing the page with devtools open does not leak the old
+// windows from previous navigations.
+//
+// IF THIS TEST STARTS FAILING, YOU ARE LEAKING EVERY WINDOW EVER NAVIGATED TO
+// WHILE DEVTOOLS ARE OPEN! THIS IS NOT SPECIFIC TO THE MEMORY TOOL ONLY!
+
+"use strict";
+
+const {
+  getLabelAndShallowSize,
+} = require("resource://devtools/shared/heapsnapshot/DominatorTreeNode.js");
+
+const TEST_URL =
+  "http://example.com/browser/devtools/client/memory/test/browser/doc_empty.html";
+
+async function getWindowsInSnapshot(front) {
+  dumpn("Taking snapshot.");
+  const path = await front.saveHeapSnapshot();
+  dumpn("Took snapshot with path = " + path);
+  const snapshot = ChromeUtils.readHeapSnapshot(path);
+  dumpn("Read snapshot into memory, taking census.");
+  const report = snapshot.takeCensus({
+    breakdown: {
+      by: "objectClass",
+      then: { by: "bucket" },
+      other: { by: "count", count: true, bytes: false },
+    },
+  });
+  dumpn("Took census, window count = " + report.Window.count);
+  return report.Window;
+}
+
+const DESCRIPTION = {
+  by: "coarseType",
+  objects: {
+    by: "objectClass",
+    then: { by: "count", count: true, bytes: false },
+    other: { by: "count", count: true, bytes: false },
+  },
+  strings: { by: "count", count: true, bytes: false },
+  scripts: {
+    by: "internalType",
+    then: { by: "count", count: true, bytes: false },
+  },
+  other: {
+    by: "internalType",
+    then: { by: "count", count: true, bytes: false },
+  },
+};
+
+this.test = makeMemoryTest(TEST_URL, async function ({ tab, panel }) {
+  let front = panel.panelWin.gStore.getState().front;
+
+  const startWindows = await getWindowsInSnapshot(front);
+  dumpn(
+    "Initial windows found = " +
+      startWindows.map(w => "0x" + w.toString(16)).join(", ")
+  );
+  is(startWindows.length, 1);
+
+  await reloadBrowser();
+
+  // Update the front as we may have switched to a new target and a new memory front
+  front = panel.panelWin.gStore.getState().front;
+
+  const endWindows = await getWindowsInSnapshot(front);
+  is(endWindows.length, 1);
+
+  if (endWindows.length === 1) {
+    return;
+  }
+
+  dumpn("Test failed, diagnosing leaking windows.");
+  dumpn(
+    "(This may fail if a moving GC has relocated the initial Window objects.)"
+  );
+
+  dumpn("Taking full runtime snapshot.");
+  const path = await front.saveHeapSnapshot({ boundaries: { runtime: true } });
+  dumpn("Full runtime's snapshot path = " + path);
+
+  dumpn("Reading full runtime heap snapshot.");
+  const snapshot = ChromeUtils.readHeapSnapshot(path);
+  dumpn("Done reading full runtime heap snapshot.");
+
+  const dominatorTree = snapshot.computeDominatorTree();
+  const paths = snapshot.computeShortestPaths(
+    dominatorTree.root,
+    startWindows,
+    50
+  );
+
+  for (let i = 0; i < startWindows.length; i++) {
+    dumpn(
+      "Shortest retaining paths for leaking Window 0x" +
+        startWindows[i].toString(16) +
+        " ========================="
+    );
+    let j = 0;
+    for (const retainingPath of paths.get(startWindows[i])) {
+      if (retainingPath.find(part => part.predecessor === startWindows[i])) {
+        // Skip paths that loop out from the target window and back to it again.
+        continue;
+      }
+
+      dumpn(
+        "    Path #" +
+          ++j +
+          ": --------------------------------------------------------------------"
+      );
+      for (const part of retainingPath) {
+        const { label } = getLabelAndShallowSize(
+          part.predecessor,
+          snapshot,
+          DESCRIPTION
+        );
+        dumpn(
+          "        0x" +
+            part.predecessor.toString(16) +
+            " (" +
+            label.join(" > ") +
+            ")"
+        );
+        dumpn("               |");
+        dumpn("              " + part.edge);
+        dumpn("               |");
+        dumpn("               V");
+      }
+      dumpn(
+        "        0x" + startWindows[i].toString(16) + " (objects > Window)"
+      );
+    }
+  }
+});