Bug 1646088 - Part 3: Add a test for slow process switches, r=kmag

Differential Revision: https://phabricator.services.mozilla.com/D79890
2020-06-17 15:43:39 +00:00 · 2020-06-17 15:43:39 +00:00 · f238179d45
--- a/dom/ipc/tests/browser.ini
+++ b/dom/ipc/tests/browser.ini
@ -20,3 +20,6 @@ skip-if = !e10s
 [browser_ElapsedTime.js]
 support-files = elapsed_time.sjs
 skip-if = (debug && os == "linux" && os_version == "18.04") || (!debug && os == "win") #Bug 1591344
+[browser_bug1646088.js]
+support-files = file_dummy.html
+skip-if = !e10s
--- a/dom/ipc/tests/browser_bug1646088.js
+++ b/dom/ipc/tests/browser_bug1646088.js
@ -0,0 +1,70 @@
+const { PromiseUtils } = ChromeUtils.import(
+  "resource://gre/modules/PromiseUtils.jsm"
+);
+
+let dir = getChromeDir(getResolvedURI(gTestPath));
+dir.append("file_dummy.html");
+const uriString = Services.io.newFileURI(dir).spec;
+
+add_task(async function() {
+  await BrowserTestUtils.withNewTab("https://example.com", async function(
+    browser
+  ) {
+    // Override the browser's `prepareToChangeRemoteness` so that we can delay
+    // the process switch for an indefinite amount of time. This will allow us
+    // to control the timing of the resolve call to trigger the bug.
+    let prepareToChangeCalled = PromiseUtils.defer();
+    let finishSwitch = PromiseUtils.defer();
+    let oldPrepare = browser.prepareToChangeRemoteness;
+    browser.prepareToChangeRemoteness = async () => {
+      prepareToChangeCalled.resolve();
+      await oldPrepare.call(browser);
+      await finishSwitch.promise;
+    };
+
+    // Begin a process switch, which should cause `prepareToChangeRemoteness` to
+    // be called. We do this from the content process to make sure the frontend
+    // has no chance to trigger an eager process switch.
+    info("Beginning process switch into file URI process");
+    let browserLoaded = BrowserTestUtils.browserLoaded(browser);
+    await SpecialPowers.spawn(browser, [uriString], uri => {
+      content.location = uri;
+    });
+    await prepareToChangeCalled.promise;
+
+    // The tab we opened is now midway through process switching. Open another
+    // browser within the same tab, and immediately close it after the load
+    // finishes.
+    info("Creating new tab loaded in file URI process");
+    let fileProcess;
+    let browserParentDestroyed = PromiseUtils.defer();
+    await BrowserTestUtils.withNewTab(uriString, async function(otherBrowser) {
+      let remoteTab = otherBrowser.frameLoader.remoteTab;
+      fileProcess = remoteTab.contentProcessId;
+      info("Loaded test URI in pid: " + fileProcess);
+
+      browserParentDestroyed.resolve(
+        TestUtils.topicObserved(
+          "ipc:browser-destroyed",
+          subject => subject === remoteTab
+        )
+      );
+    });
+    await browserParentDestroyed.promise;
+
+    // This browser has now been closed, which could cause the file content
+    // process to begin shutting down, despite us process switching into it.
+    // We can now allow the process switch to finish, and wait for the load to
+    // finish as well.
+    info("BrowserParent has been destroyed, finishing process switch");
+    finishSwitch.resolve();
+    await browserLoaded;
+
+    info("Load complete");
+    is(
+      browser.frameLoader.remoteTab.contentProcessId,
+      fileProcess,
+      "Should have loaded in the same file URI process"
+    );
+  });
+});
--- a/dom/ipc/tests/file_dummy.html
+++ b/dom/ipc/tests/file_dummy.html
@ -0,0 +1,4 @@
+<!doctype html>
+<body>
+  <h1>This is a dummy file</h1>
+</body>