diff --git a/dom/audiochannel/AudioChannelAgent.cpp b/dom/audiochannel/AudioChannelAgent.cpp
index 31a6cc14032a..ac46b5c049b6 100644
--- a/dom/audiochannel/AudioChannelAgent.cpp
+++ b/dom/audiochannel/AudioChannelAgent.cpp
@@ -6,11 +6,7 @@
 
 #include "AudioChannelAgent.h"
 #include "AudioChannelService.h"
-#include "mozilla/Preferences.h"
-#include "nsIAppsService.h"
-#include "nsIDocument.h"
 #include "nsIDOMWindow.h"
-#include "nsIPrincipal.h"
 #include "nsPIDOMWindow.h"
 #include "nsXULAppAPI.h"
 
@@ -81,81 +77,6 @@ AudioChannelAgent::InitWithWeakCallback(nsIDOMWindow* aWindow,
                       /* useWeakRef = */ true);
 }
 
-nsresult
-AudioChannelAgent::FindCorrectWindow(nsIDOMWindow* aWindow)
-{
-  nsCOMPtr<nsPIDOMWindow> window = do_QueryInterface(aWindow);
-  MOZ_ASSERT(window->IsInnerWindow());
-
-  mWindow = window->GetScriptableTop();
-  if (NS_WARN_IF(!mWindow)) {
-    return NS_OK;
-  }
-
-  mWindow = mWindow->GetOuterWindow();
-  if (NS_WARN_IF(!mWindow)) {
-    return NS_ERROR_FAILURE;
-  }
-
-  // From here we do an hack for nested iframes.
-  // The system app doesn't have access to the nested iframe objects so it
-  // cannot control the volume of the agents running in nested apps. What we do
-  // here is to assign those Agents to the top scriptable window of the parent
-  // iframe (what is controlled by the system app).
-  // For doing this we go recursively back into the chain of windows until we
-  // find apps that are not the system one.
-  window = mWindow->GetParent();
-  if (!window || window == mWindow) {
-    return NS_OK;
-  }
-
-  window = window->GetCurrentInnerWindow();
-  if (!window) {
-    return NS_OK;
-  }
-
-  nsCOMPtr<nsIDocument> doc = window->GetExtantDoc();
-  if (!doc) {
-    return NS_OK;
-  }
-
-  nsCOMPtr<nsIPrincipal> principal = doc->NodePrincipal();
-
-  uint32_t appId;
-  nsresult rv = principal->GetAppId(&appId);
-  if (NS_WARN_IF(NS_FAILED(rv))) {
-    return rv;
-  }
-
-  if (appId == nsIScriptSecurityManager::NO_APP_ID ||
-      appId == nsIScriptSecurityManager::UNKNOWN_APP_ID) {
-    return NS_OK;
-  }
-
-  nsCOMPtr<nsIAppsService> appsService = do_GetService(APPS_SERVICE_CONTRACTID);
-  if (NS_WARN_IF(!appsService)) {
-    return NS_ERROR_FAILURE;
-  }
-
-  nsAdoptingString systemAppManifest =
-    mozilla::Preferences::GetString("b2g.system_manifest_url");
-  if (!systemAppManifest) {
-    return NS_OK;
-  }
-
-  uint32_t systemAppId;
-  rv = appsService->GetAppLocalIdByManifestURL(systemAppManifest, &systemAppId);
-  if (NS_WARN_IF(NS_FAILED(rv))) {
-    return rv;
-  }
-
-  if (systemAppId == appId) {
-    return NS_OK;
-  }
-
-  return FindCorrectWindow(window);
-}
-
 nsresult
 AudioChannelAgent::InitInternal(nsIDOMWindow* aWindow, int32_t aChannelType,
                                 nsIAudioChannelAgentCallback *aCallback,
@@ -187,9 +108,18 @@ AudioChannelAgent::InitInternal(nsIDOMWindow* aWindow, int32_t aChannelType,
   MOZ_ASSERT(pInnerWindow->IsInnerWindow());
   mInnerWindowID = pInnerWindow->WindowID();
 
-  nsresult rv = FindCorrectWindow(aWindow);
-  if (NS_WARN_IF(NS_FAILED(rv))) {
-    return rv;
+  nsCOMPtr<nsPIDOMWindow> topWindow = pInnerWindow->GetScriptableTop();
+  if (NS_WARN_IF(!topWindow)) {
+    return NS_OK;
+  }
+
+  mWindow = do_QueryInterface(topWindow);
+  if (mWindow) {
+    mWindow = mWindow->GetOuterWindow();
+  }
+
+  if (NS_WARN_IF(!mWindow)) {
+    return NS_ERROR_FAILURE;
   }
 
   mAudioChannelType = aChannelType;
diff --git a/dom/audiochannel/AudioChannelAgent.h b/dom/audiochannel/AudioChannelAgent.h
index 9487b33aef97..74271199ec8a 100644
--- a/dom/audiochannel/AudioChannelAgent.h
+++ b/dom/audiochannel/AudioChannelAgent.h
@@ -56,8 +56,6 @@ private:
 
   void Shutdown();
 
-  nsresult FindCorrectWindow(nsIDOMWindow* aWindow);
-
   nsCOMPtr<nsPIDOMWindow> mWindow;
   nsCOMPtr<nsIAudioChannelAgentCallback> mCallback;
 
diff --git a/dom/browser-element/mochitest/browserElement_AudioChannel.js b/dom/browser-element/mochitest/browserElement_AudioChannel.js
index 38ff10a2b622..d5e8a3da9c03 100644
--- a/dom/browser-element/mochitest/browserElement_AudioChannel.js
+++ b/dom/browser-element/mochitest/browserElement_AudioChannel.js
@@ -192,10 +192,7 @@ function runTests() {
 }
 
 
-addEventListener('testready', function() {
-  SpecialPowers.pushPrefEnv({'set': [["b2g.system_manifest_url", "http://mochi.test:8888/manifest.webapp"]]},
-                            function() {
-    SimpleTest.executeSoon(runTests);
-  });
+addEventListener('load', function() {
+  SimpleTest.executeSoon(runTests);
 });
 
diff --git a/dom/browser-element/mochitest/browserElement_AudioChannel_nested.js b/dom/browser-element/mochitest/browserElement_AudioChannel_nested.js
index 226d6377ff0b..54b0d4047561 100644
--- a/dom/browser-element/mochitest/browserElement_AudioChannel_nested.js
+++ b/dom/browser-element/mochitest/browserElement_AudioChannel_nested.js
@@ -72,8 +72,5 @@ function runTests() {
 }
 
 addEventListener('testready', function() {
-  SpecialPowers.pushPrefEnv({'set': [["b2g.system_manifest_url", "http://mochi.test:8888/manifest.webapp"]]},
-                            function() {
-    SimpleTest.executeSoon(runTests);
-  });
+  SimpleTest.executeSoon(runTests);
 });
diff --git a/dom/browser-element/mochitest/browserElement_AudioPlayback.js b/dom/browser-element/mochitest/browserElement_AudioPlayback.js
index 8a8b5e7a828f..42dba665c8ab 100644
--- a/dom/browser-element/mochitest/browserElement_AudioPlayback.js
+++ b/dom/browser-element/mochitest/browserElement_AudioPlayback.js
@@ -68,9 +68,4 @@ function runTest() {
   iframe.src = browserElementTestHelpers.emptyPage1;
 }
 
-addEventListener('testready', function() {
-  SpecialPowers.pushPrefEnv({'set': [["b2g.system_manifest_url", "http://mochi.test:8888/manifest.webapp"]]},
-                            function() {
-    SimpleTest.executeSoon(runTest);
-  });
-});
+addEventListener('testready', runTest);