diff --git a/caps/idl/nsIPrincipal.idl b/caps/idl/nsIPrincipal.idl
index 54a0901d36e2..538b5be18a2e 100644
--- a/caps/idl/nsIPrincipal.idl
+++ b/caps/idl/nsIPrincipal.idl
@@ -184,47 +184,17 @@ interface nsIPrincipal : nsISerializable
      */
     readonly attribute unsigned long appId;
 
-    %{C++
-    uint32_t GetAppId()
-    {
-      uint32_t appId;
-      mozilla::DebugOnly<nsresult> rv = GetAppId(&appId);
-      MOZ_ASSERT(NS_SUCCEEDED(rv));
-      return appId;
-    }
-    %}
-
     /**
      * Returns true iif the principal is inside a browser element.
      */
     readonly attribute boolean isInBrowserElement;
 
-    %{C++
-    bool GetIsInBrowserElement()
-    {
-      bool isInBrowserElement;
-      mozilla::DebugOnly<nsresult> rv = GetIsInBrowserElement(&isInBrowserElement);
-      MOZ_ASSERT(NS_SUCCEEDED(rv));
-      return isInBrowserElement;
-    }
-    %}
-
     /**
      * Returns true if this principal has an unknown appId. This shouldn't
      * generally be used. We only expose it due to not providing the correct
      * appId everywhere where we construct principals.
      */
     readonly attribute boolean unknownAppId;
-
-    %{C++
-    bool GetUnknownAppId()
-    {
-      bool unkwnownAppId;
-      mozilla::DebugOnly<nsresult> rv = GetIsInBrowserElement(&unkwnownAppId);
-      MOZ_ASSERT(NS_SUCCEEDED(rv));
-      return unkwnownAppId;
-    }
-    %}
 };
 
 /**
diff --git a/caps/include/nsScriptSecurityManager.h b/caps/include/nsScriptSecurityManager.h
index a272d83e8e2b..f4f2d73d43ba 100644
--- a/caps/include/nsScriptSecurityManager.h
+++ b/caps/include/nsScriptSecurityManager.h
@@ -348,22 +348,6 @@ public:
         return sStrictFileOriginPolicy;
     }
 
-    /**
-     * Returns true if the two principals share the same app attributes.
-     *
-     * App attributes are appId and the inBrowserElement flag.
-     * Two principals have the same app attributes if those information are
-     * equals.
-     * This method helps keeping principals from different apps isolated from
-     * each other. Also, it helps making sure mozbrowser (web views) and their
-     * parent are isolated from each other. All those entities do not share the
-     * same data (cookies, IndexedDB, localStorage, etc.) so we shouldn't allow
-     * violating that principle.
-     */
-    static bool
-    AppAttributesEqual(nsIPrincipal* aFirst,
-                       nsIPrincipal* aSecond);
-
 private:
 
     // GetScriptSecurityManager is the only call that can make one
diff --git a/caps/src/nsPrincipal.cpp b/caps/src/nsPrincipal.cpp
index 3834cb96e2b6..b6df185609ba 100644
--- a/caps/src/nsPrincipal.cpp
+++ b/caps/src/nsPrincipal.cpp
@@ -263,42 +263,34 @@ nsPrincipal::GetOrigin(char **aOrigin)
 NS_IMETHODIMP
 nsPrincipal::Equals(nsIPrincipal *aOther, bool *aResult)
 {
-  *aResult = false;
-
   if (!aOther) {
     NS_WARNING("Need a principal to compare this to!");
+    *aResult = false;
     return NS_OK;
   }
 
-  if (aOther == this) {
-    *aResult = true;
+  if (this != aOther) {
+
+    // Codebases are equal if they have the same origin.
+    *aResult =
+      NS_SUCCEEDED(nsScriptSecurityManager::CheckSameOriginPrincipal(this,
+                                                                     aOther));
     return NS_OK;
   }
 
-  // Codebases are equal if they have the same origin.
-  *aResult = NS_SUCCEEDED(
-               nsScriptSecurityManager::CheckSameOriginPrincipal(this, aOther));
+  *aResult = true;
   return NS_OK;
 }
 
 NS_IMETHODIMP
 nsPrincipal::EqualsIgnoringDomain(nsIPrincipal *aOther, bool *aResult)
 {
-  *aResult = false;
-
-  if (!aOther) {
-    NS_WARNING("Need a principal to compare this to!");
-    return NS_OK;
-  }
-
-  if (aOther == this) {
+  if (this == aOther) {
     *aResult = true;
     return NS_OK;
   }
 
-  if (!nsScriptSecurityManager::AppAttributesEqual(this, aOther)) {
-    return NS_OK;
-  }
+  *aResult = false;
 
   nsCOMPtr<nsIURI> otherURI;
   nsresult rv = aOther->GetURI(getter_AddRefs(otherURI));
diff --git a/caps/src/nsScriptSecurityManager.cpp b/caps/src/nsScriptSecurityManager.cpp
index 8bc6420ad8da..e265351b45a0 100644
--- a/caps/src/nsScriptSecurityManager.cpp
+++ b/caps/src/nsScriptSecurityManager.cpp
@@ -890,10 +890,6 @@ nsScriptSecurityManager::CheckSameOriginPrincipal(nsIPrincipal* aSubject,
     if (aSubject == aObject)
         return NS_OK;
 
-    if (!AppAttributesEqual(aSubject, aObject)) {
-        return NS_ERROR_DOM_PROP_ACCESS_DENIED;
-    }
-
     // Default to false, and change if that turns out wrong.
     bool subjectSetDomain = false;
     bool objectSetDomain = false;
@@ -954,26 +950,6 @@ nsScriptSecurityManager::HashPrincipalByOrigin(nsIPrincipal* aPrincipal)
     return SecurityHashURI(uri);
 }
 
-/* static */ bool
-nsScriptSecurityManager::AppAttributesEqual(nsIPrincipal* aFirst,
-                                            nsIPrincipal* aSecond)
-{
-    MOZ_ASSERT(aFirst && aSecond, "Don't pass null pointers!");
-
-    uint32_t firstAppId = nsIScriptSecurityManager::UNKNOWN_APP_ID;
-    if (!aFirst->GetUnknownAppId()) {
-        firstAppId = aFirst->GetAppId();
-    }
-
-    uint32_t secondAppId = nsIScriptSecurityManager::UNKNOWN_APP_ID;
-    if (!aSecond->GetUnknownAppId()) {
-        secondAppId = aSecond->GetAppId();
-    }
-
-    return ((firstAppId == secondAppId) &&
-            (aFirst->GetIsInBrowserElement() == aSecond->GetIsInBrowserElement()));
-}
-
 nsresult
 nsScriptSecurityManager::CheckSameOriginDOMProp(nsIPrincipal* aSubject,
                                                 nsIPrincipal* aObject,
diff --git a/caps/tests/mochitest/Makefile.in b/caps/tests/mochitest/Makefile.in
index fa748a8c4a4e..c7d0b47a7627 100644
--- a/caps/tests/mochitest/Makefile.in
+++ b/caps/tests/mochitest/Makefile.in
@@ -16,7 +16,6 @@ MOCHITEST_FILES = 	test_bug423375.html \
                 test_bug292789.html \
                 test_bug470804.html \
                 test_disallowInheritPrincipal.html \
-                test_app_principal_equality.html \
                 $(NULL)
 
 # extendedOrigin test doesn't work on Windows, see bug 776296.
diff --git a/caps/tests/mochitest/test_app_principal_equality.html b/caps/tests/mochitest/test_app_principal_equality.html
deleted file mode 100644
index 2dddc55c0999..000000000000
--- a/caps/tests/mochitest/test_app_principal_equality.html
+++ /dev/null
@@ -1,85 +0,0 @@
-<!DOCTYPE HTML>
-<html>
-<!--
-https://bugzilla.mozilla.org/show_bug.cgi?id=777467
--->
-<head>
-  <meta charset="utf-8">
-  <title>Test app principal's equality</title>
-  <script type="application/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
-  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
-</head>
-<body>
-<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=777467">Mozilla Bug 777467</a>
-<p id="display"></p>
-<script>
-  // Initialization.
-  SpecialPowers.addPermission("browser", true, document);
-  SpecialPowers.addPermission("embed-apps", true, document);
-
-  var previousPrefs = {
-    mozBrowserFramesEnabled: undefined,
-    oop_by_default: undefined,
-  };
-  try {
-    previousPrefs.mozBrowserFramesEnabled = SpecialPowers.getBoolPref('dom.mozBrowserFramesEnabled');
-  } catch(e) {}
-
-  try {
-    previousPrefs.oop_by_default = SpecialPowers.getBoolPref('dom.ipc.browser_frames.oop_by_default');
-  } catch(e) {}
-
-  SpecialPowers.setBoolPref('dom.mozBrowserFramesEnabled', true);
-  SpecialPowers.setBoolPref("dom.ipc.browser_frames.oop_by_default", false);
-</script>
-<div id="content" style="display: none;">
-  <iframe src="error404"></iframe>
-  <iframe mozbrowser src="error404"></iframe>
-  <iframe mozapp="http://example.org/manifest.webapp" mozbrowser src="error404"></iframe>
-</div>
-<pre id="test">
-<script type="application/javascript">
-
-/** Test for app principal's equality **/
-
-SimpleTest.waitForExplicitFinish();
-
-function canAccessDocument(win) {
-  var result = true;
-  try {
-    win.document;
-  } catch(e) {
-    result = false;
-  }
-  return result;
-}
-
-addLoadEvent(function() {
-  // Test the witness frame (we can access same-origin frame).
-  is(canAccessDocument(frames[0]), true,
-     "should be able to access the first frame");
-
-  // Test different app/browserElement frames.
-  for (var i=1; i<frames.length; ++i) {
-    is(canAccessDocument(frames[i]), false,
-       "should not be able to access the other frames");
-  }
-
-  // Cleanup.
-  if (previousPrefs.mozBrowserFramesEnabled !== undefined) {
-    SpecialPowers.setBoolPref('dom.mozBrowserFramesEnabled', previousPrefs.mozBrowserFramesEnabled);
-  }
-  if (previousPrefs.oop_by_default !== undefined) {
-    SpecialPowers.setBoolPref("dom.ipc.browser_frames.oop_by_default", previousPrefs.oop_by_default);
-  }
-
-  SpecialPowers.removePermission("browser", window.document);
-  SpecialPowers.removePermission("embed-apps", window.document);
-
-  SimpleTest.finish();
-});
-
-</script>
-</pre>
-</body>
-</html>