diff --git a/browser/base/content/test/plugins/browser_pluginCrashCommentAndURL.js b/browser/base/content/test/plugins/browser_pluginCrashCommentAndURL.js
index f8373abd6973..03800fbaf6dc 100644
--- a/browser/base/content/test/plugins/browser_pluginCrashCommentAndURL.js
+++ b/browser/base/content/test/plugins/browser_pluginCrashCommentAndURL.js
@@ -1,5 +1,4 @@
 Cu.import("resource://gre/modules/CrashSubmit.jsm", this);
-Cu.import("resource://gre/modules/PromiseUtils.jsm");
 
 const SERVER_URL = "http://example.com/browser/toolkit/crashreporter/test/browser/crashreport.sjs";
 
@@ -7,8 +6,6 @@ var gTestRoot = getRootDirectory(gTestPath).replace("chrome://mochitests/content
 var gTestBrowser = null;
 var config = {};
 
-let gRegisteredCrashObserver = null;
-
 add_task(async function() {
   // The test harness sets MOZ_CRASHREPORTER_NO_REPORT, which disables plugin
   // crash reports.  This test needs them enabled.  The test also needs a mock
@@ -30,9 +27,6 @@ add_task(async function() {
 
   registerCleanupFunction(async function() {
     Services.prefs.clearUserPref("dom.ipc.plugins.timeoutSecs");
-    if (gRegisteredCrashObserver !== null) {
-      Services.obs.removeObserver(gRegisteredCrashObserver, "plugin-crashed");
-    }
     env.set("MOZ_CRASHREPORTER_NO_REPORT", noReport);
     env.set("MOZ_CRASHREPORTER_URL", serverUrl);
     env = null;
@@ -119,25 +113,6 @@ add_task(async function() {
 });
 
 add_task(async function() {
-  // Since this test doesn't actually submit a crash report, we can't await
-  // on crashReportStatus. This ensures the crash handling mechanism is
-  // completely finished before exiting the test.
-  let crashObserverDeferred = PromiseUtils.defer();
-
-  gRegisteredCrashObserver = (subject, topic, data) => {
-    if (topic != "plugin-crashed") {
-      return;
-    }
-    let propBag = subject.QueryInterface(Ci.nsIPropertyBag2);
-    let minidumpID = propBag.getPropertyAsAString("pluginDumpID");
-
-    Services.crashmanager.ensureCrashIsPresent(minidumpID).then(() => {
-      crashObserverDeferred.resolve();
-    });
-  };
-
-  Services.obs.addObserver(gRegisteredCrashObserver, "plugin-crashed");
-
   config = {
     shouldSubmissionUIBeVisible: false,
     comment: "",
@@ -166,8 +141,6 @@ add_task(async function() {
     Assert.equal(!!pleaseSubmit && content.getComputedStyle(pleaseSubmit).display == "block",
       aConfig.shouldSubmissionUIBeVisible, "Plugin crash UI should not be visible");
   });
-
-  await crashObserverDeferred.promise;
 });
 
 function promisePluginCrashed() {
diff --git a/browser/base/content/test/plugins/browser_pluginCrashReportNonDeterminism.js b/browser/base/content/test/plugins/browser_pluginCrashReportNonDeterminism.js
index 9519d16bd274..72863d6a7ad5 100644
--- a/browser/base/content/test/plugins/browser_pluginCrashReportNonDeterminism.js
+++ b/browser/base/content/test/plugins/browser_pluginCrashReportNonDeterminism.js
@@ -1,8 +1,6 @@
 /* Any copyright is dedicated to the Public Domain.
  * http://creativecommons.org/publicdomain/zero/1.0/ */
 
-Cu.import("resource://gre/modules/PromiseUtils.jsm");
-
 /**
  * With e10s, plugins must run in their own process. This means we have
  * three processes at a minimum when we're running a plugin:
@@ -81,9 +79,6 @@ function preparePlugin(browser, pluginFallbackState) {
   });
 }
 
-// Allows tests to ensure crash handling is completely finished before exiting.
-let crashObserverDeferred = PromiseUtils.defer();
-
 add_task(async function setup() {
   // Bypass click-to-play
   setTestPluginEnabledState(Ci.nsIPluginTag.STATE_ENABLED);
@@ -113,10 +108,6 @@ add_task(async function setup() {
 
       pluginDumpFile.remove(false);
       extraFile.remove(false);
-
-      // Resolve and replace the deferred object so the next test can wait on it
-      crashObserverDeferred.resolve();
-      crashObserverDeferred = PromiseUtils.defer();
     });
   };
 
@@ -192,7 +183,6 @@ add_task(async function testChromeHearsPluginCrashFirst() {
       "Should have been showing crash report UI");
   });
   await BrowserTestUtils.closeWindow(win);
-  await crashObserverDeferred.promise;
 });
 
 /**
@@ -263,5 +253,4 @@ add_task(async function testContentHearsCrashFirst() {
   });
 
   await BrowserTestUtils.closeWindow(win);
-  await crashObserverDeferred.promise;
 });