diff --git a/dom/html/nsFormSubmission.cpp b/dom/html/nsFormSubmission.cpp
index ea4df705dbd6..9d46b980b8b9 100644
--- a/dom/html/nsFormSubmission.cpp
+++ b/dom/html/nsFormSubmission.cpp
@@ -848,7 +848,6 @@ GetSubmissionFromForm(nsGenericHTMLElement* aForm,
     *aFormSubmission = new nsFSURLEncoded(charset, method, doc,
                                           aOriginatingElement);
   }
-  NS_ENSURE_TRUE(*aFormSubmission, NS_ERROR_OUT_OF_MEMORY);
 
   return NS_OK;
 }
diff --git a/dom/json/nsJSON.cpp b/dom/json/nsJSON.cpp
index 910792bf5427..954a6ad5abb5 100644
--- a/dom/json/nsJSON.cpp
+++ b/dom/json/nsJSON.cpp
@@ -298,8 +298,6 @@ nsJSONWriter::Write(const char16_t *aBuffer, uint32_t aLength)
 
   if (!mDidWrite) {
     mBuffer = new char16_t[JSON_STREAM_BUFSIZE];
-    if (!mBuffer)
-      return NS_ERROR_OUT_OF_MEMORY;
     mDidWrite = true;
   }
 
@@ -481,9 +479,6 @@ nsresult
 NS_NewJSON(nsISupports* aOuter, REFNSIID aIID, void** aResult)
 {
   nsJSON* json = new nsJSON();
-  if (!json)
-    return NS_ERROR_OUT_OF_MEMORY;
-
   NS_ADDREF(json);
   *aResult = json;
 
diff --git a/dom/jsurl/nsJSProtocolHandler.cpp b/dom/jsurl/nsJSProtocolHandler.cpp
index 991fbe214ba4..b30fdcb75f2e 100644
--- a/dom/jsurl/nsJSProtocolHandler.cpp
+++ b/dom/jsurl/nsJSProtocolHandler.cpp
@@ -410,8 +410,6 @@ nsresult nsJSChannel::Init(nsIURI *aURI)
 
     // Create the nsIStreamIO layer used by the nsIStreamIOChannel.
     mIOThunk = new nsJSThunk();
-    if (!mIOThunk)
-        return NS_ERROR_OUT_OF_MEMORY;
 
     // Create a stock input stream channel...
     // Remember, until AsyncOpen is called, the script will not be evaluated
@@ -1129,8 +1127,6 @@ nsJSProtocolHandler::Create(nsISupports *aOuter, REFNSIID aIID, void **aResult)
         return NS_ERROR_NO_AGGREGATION;
 
     nsJSProtocolHandler* ph = new nsJSProtocolHandler();
-    if (!ph)
-        return NS_ERROR_OUT_OF_MEMORY;
     NS_ADDREF(ph);
     nsresult rv = ph->Init();
     if (NS_SUCCEEDED(rv)) {
diff --git a/dom/media/MediaCache.cpp b/dom/media/MediaCache.cpp
index ce39cce3d91c..0ebe1578fd12 100644
--- a/dom/media/MediaCache.cpp
+++ b/dom/media/MediaCache.cpp
@@ -640,9 +640,6 @@ InitMediaCache()
     return;
 
   gMediaCache = new MediaCache();
-  if (!gMediaCache)
-    return;
-
   nsresult rv = gMediaCache->Init();
   if (NS_FAILED(rv)) {
     delete gMediaCache;
diff --git a/dom/media/MediaResource.cpp b/dom/media/MediaResource.cpp
index bc28f31baa7b..9b8ab4b89df4 100644
--- a/dom/media/MediaResource.cpp
+++ b/dom/media/MediaResource.cpp
@@ -549,8 +549,6 @@ nsresult ChannelMediaResource::OpenChannel(nsIStreamListener** aStreamListener)
   }
 
   mListener = new Listener(this);
-  NS_ENSURE_TRUE(mListener, NS_ERROR_OUT_OF_MEMORY);
-
   if (aStreamListener) {
     *aStreamListener = mListener;
     NS_ADDREF(*aStreamListener);
diff --git a/dom/plugins/base/nsNPAPIPluginInstance.cpp b/dom/plugins/base/nsNPAPIPluginInstance.cpp
index b93086833429..eaa7f697a68a 100644
--- a/dom/plugins/base/nsNPAPIPluginInstance.cpp
+++ b/dom/plugins/base/nsNPAPIPluginInstance.cpp
@@ -582,9 +582,6 @@ nsNPAPIPluginInstance::NewStreamFromPlugin(const char* type, const char* target,
                                            nsIOutputStream* *result)
 {
   nsPluginStreamToFile* stream = new nsPluginStreamToFile(target, mOwner);
-  if (!stream)
-    return NS_ERROR_OUT_OF_MEMORY;
-
   return stream->QueryInterface(kIOutputStreamIID, (void**)result);
 }
 
diff --git a/dom/plugins/base/nsPluginHost.cpp b/dom/plugins/base/nsPluginHost.cpp
index 7b1d36b4754f..1933ab076592 100644
--- a/dom/plugins/base/nsPluginHost.cpp
+++ b/dom/plugins/base/nsPluginHost.cpp
@@ -2227,9 +2227,6 @@ nsresult nsPluginHost::ScanPluginsDirectory(nsIFile *pluginsDir,
 
       pluginTag = new nsPluginTag(&info, fileModTime, fromExtension);
       pluginFile.FreePluginInfo(info);
-      if (!pluginTag)
-        return NS_ERROR_OUT_OF_MEMORY;
-
       pluginTag->mLibrary = library;
       uint32_t state;
       rv = pluginTag->GetBlocklistState(&state);
@@ -3319,8 +3316,6 @@ nsPluginHost::EnsurePrivateDirServiceProvider()
   if (!mPrivateDirServiceProvider) {
     nsresult rv;
     mPrivateDirServiceProvider = new nsPluginDirServiceProvider();
-    if (!mPrivateDirServiceProvider)
-      return NS_ERROR_OUT_OF_MEMORY;
     nsCOMPtr<nsIDirectoryService> dirService(do_GetService(kDirectoryServiceContractID, &rv));
     if (NS_FAILED(rv))
       return rv;
diff --git a/dom/plugins/base/nsPluginInstanceOwner.cpp b/dom/plugins/base/nsPluginInstanceOwner.cpp
index 1e1fde16e233..2ccd41de8aae 100644
--- a/dom/plugins/base/nsPluginInstanceOwner.cpp
+++ b/dom/plugins/base/nsPluginInstanceOwner.cpp
@@ -1150,9 +1150,6 @@ void nsPluginInstanceOwner::AddToCARefreshTimer() {
 
   if (!sCARefreshListeners) {
     sCARefreshListeners = new nsTArray<nsPluginInstanceOwner*>();
-    if (!sCARefreshListeners) {
-      return;
-    }
   }
 
   if (sCARefreshListeners->Contains(this)) {
@@ -1163,9 +1160,6 @@ void nsPluginInstanceOwner::AddToCARefreshTimer() {
 
   if (!sCATimer) {
     sCATimer = new nsCOMPtr<nsITimer>();
-    if (!sCATimer) {
-      return;
-    }
   }
 
   if (sCARefreshListeners->Length() == 1) {
diff --git a/dom/plugins/base/nsPluginNativeWindow.cpp b/dom/plugins/base/nsPluginNativeWindow.cpp
index 7851819e74dc..f9baf5b813ee 100644
--- a/dom/plugins/base/nsPluginNativeWindow.cpp
+++ b/dom/plugins/base/nsPluginNativeWindow.cpp
@@ -41,7 +41,7 @@ nsresult PLUG_NewPluginNativeWindow(nsPluginNativeWindow ** aPluginNativeWindow)
 {
   NS_ENSURE_ARG_POINTER(aPluginNativeWindow);
   *aPluginNativeWindow = new nsPluginNativeWindowPLATFORM();
-  return *aPluginNativeWindow ? NS_OK : NS_ERROR_OUT_OF_MEMORY;
+  return NS_OK;
 }
 
 nsresult PLUG_DeletePluginNativeWindow(nsPluginNativeWindow * aPluginNativeWindow)
diff --git a/dom/plugins/base/nsPluginNativeWindowGtk.cpp b/dom/plugins/base/nsPluginNativeWindowGtk.cpp
index 4d2865e25e31..f3180c9d7b89 100644
--- a/dom/plugins/base/nsPluginNativeWindowGtk.cpp
+++ b/dom/plugins/base/nsPluginNativeWindowGtk.cpp
@@ -57,7 +57,7 @@ nsresult PLUG_NewPluginNativeWindow(nsPluginNativeWindow ** aPluginNativeWindow)
 {
   NS_ENSURE_ARG_POINTER(aPluginNativeWindow);
   *aPluginNativeWindow = new nsPluginNativeWindowGtk();
-  return *aPluginNativeWindow ? NS_OK : NS_ERROR_OUT_OF_MEMORY;
+  return NS_OK;
 }
 
 nsresult PLUG_DeletePluginNativeWindow(nsPluginNativeWindow * aPluginNativeWindow)
diff --git a/dom/plugins/base/nsPluginNativeWindowQt.cpp b/dom/plugins/base/nsPluginNativeWindowQt.cpp
index cb7fa488b2d2..3249842f4c31 100644
--- a/dom/plugins/base/nsPluginNativeWindowQt.cpp
+++ b/dom/plugins/base/nsPluginNativeWindowQt.cpp
@@ -62,7 +62,7 @@ nsresult PLUG_NewPluginNativeWindow(nsPluginNativeWindow **aPluginNativeWindow)
 {
   NS_ENSURE_ARG_POINTER(aPluginNativeWindow);
   *aPluginNativeWindow = new nsPluginNativeWindowQt();
-  return *aPluginNativeWindow ? NS_OK : NS_ERROR_OUT_OF_MEMORY;
+  return NS_OK;
 }
 
 nsresult PLUG_DeletePluginNativeWindow(nsPluginNativeWindow * aPluginNativeWindow)
diff --git a/dom/plugins/base/nsPluginNativeWindowWin.cpp b/dom/plugins/base/nsPluginNativeWindowWin.cpp
index dd9fcf6b3af6..72fc011cfc05 100644
--- a/dom/plugins/base/nsPluginNativeWindowWin.cpp
+++ b/dom/plugins/base/nsPluginNativeWindowWin.cpp
@@ -575,13 +575,11 @@ nsPluginNativeWindowWin::GetPluginWindowEvent(HWND aWnd, UINT aMsg, WPARAM aWPar
   if (!mCachedPluginWindowEvent)
   {
     event = new PluginWindowEvent();
-    if (!event) return nullptr;
     mCachedPluginWindowEvent = event;
   }
   else if (mCachedPluginWindowEvent->InUse())
   {
     event = new PluginWindowEvent();
-    if (!event) return nullptr;
   }
   else
   {
@@ -739,8 +737,7 @@ nsresult PLUG_NewPluginNativeWindow(nsPluginNativeWindow ** aPluginNativeWindow)
   NS_ENSURE_ARG_POINTER(aPluginNativeWindow);
 
   *aPluginNativeWindow = new nsPluginNativeWindowWin();
-
-  return *aPluginNativeWindow ? NS_OK : NS_ERROR_OUT_OF_MEMORY;
+  return NS_OK;
 }
 
 nsresult PLUG_DeletePluginNativeWindow(nsPluginNativeWindow * aPluginNativeWindow)
diff --git a/dom/plugins/base/nsPluginStreamListenerPeer.cpp b/dom/plugins/base/nsPluginStreamListenerPeer.cpp
index 62f8770d29da..de975d0d81e3 100644
--- a/dom/plugins/base/nsPluginStreamListenerPeer.cpp
+++ b/dom/plugins/base/nsPluginStreamListenerPeer.cpp
@@ -735,12 +735,7 @@ nsPluginStreamListenerPeer::RequestRead(NPByteRange* rangeList)
   } else {
     nsWeakPtr weakpeer =
     do_GetWeakReference(static_cast<nsISupportsWeakReference*>(this));
-    nsPluginByteRangeStreamListener *brrListener =
-    new nsPluginByteRangeStreamListener(weakpeer);
-    if (brrListener)
-      converter = brrListener;
-    else
-      return NS_ERROR_OUT_OF_MEMORY;
+    converter = new nsPluginByteRangeStreamListener(weakpeer);
   }
 
   mPendingRequests += numRequests;
diff --git a/dom/plugins/ipc/PluginInstanceChild.cpp b/dom/plugins/ipc/PluginInstanceChild.cpp
index 540138087b53..05006a983bc8 100644
--- a/dom/plugins/ipc/PluginInstanceChild.cpp
+++ b/dom/plugins/ipc/PluginInstanceChild.cpp
@@ -2161,9 +2161,6 @@ PluginInstanceChild::FlashThrottleMessage(HWND aWnd,
     // that's done in Destroy.
     FlashThrottleAsyncMsg* task = new FlashThrottleAsyncMsg(this,
         aWnd, aMsg, aWParam, aLParam, isWindowed);
-    if (!task)
-        return; 
-
     {
         MutexAutoLock lock(mAsyncCallMutex);
         mPendingAsyncCalls.AppendElement(task);
diff --git a/dom/plugins/ipc/PluginInstanceParent.cpp b/dom/plugins/ipc/PluginInstanceParent.cpp
index 5f0c42907f30..b6345582b982 100644
--- a/dom/plugins/ipc/PluginInstanceParent.cpp
+++ b/dom/plugins/ipc/PluginInstanceParent.cpp
@@ -1533,11 +1533,6 @@ PluginInstanceParent::GetActorForNPObject(NPObject* aObject)
     }
 
     actor = new PluginScriptableObjectParent(LocalObject);
-    if (!actor) {
-        NS_ERROR("Out of memory!");
-        return nullptr;
-    }
-
     if (!SendPPluginScriptableObjectConstructor(actor)) {
         NS_WARNING("Failed to send constructor message!");
         return nullptr;
diff --git a/dom/plugins/test/testplugin/nptest.cpp b/dom/plugins/test/testplugin/nptest.cpp
index 16be70e506f6..58aaa7aedbfb 100644
--- a/dom/plugins/test/testplugin/nptest.cpp
+++ b/dom/plugins/test/testplugin/nptest.cpp
@@ -778,8 +778,6 @@ NPP_New(NPMIMEType pluginType, NPP instance, uint16_t mode, int16_t argc, char*
 
   // set up our our instance data
   InstanceData* instanceData = new InstanceData;
-  if (!instanceData)
-    return NPERR_OUT_OF_MEMORY_ERROR;
   instanceData->npp = instance;
   instanceData->streamMode = NP_ASFILEONLY;
   instanceData->testFunction = FUNCTION_NONE;
diff --git a/dom/presentation/provider/MulticastDNSDeviceProvider.cpp b/dom/presentation/provider/MulticastDNSDeviceProvider.cpp
index b4359220a7e2..79d885743273 100644
--- a/dom/presentation/provider/MulticastDNSDeviceProvider.cpp
+++ b/dom/presentation/provider/MulticastDNSDeviceProvider.cpp
@@ -175,9 +175,6 @@ MulticastDNSDeviceProvider::Init()
   }
 
   mWrappedListener = new DNSServiceWrappedListener();
-  if (NS_WARN_IF(!mWrappedListener)) {
-    return NS_ERROR_OUT_OF_MEMORY;
-  }
   if (NS_WARN_IF(NS_FAILED(rv = mWrappedListener->SetListener(this)))) {
     return rv;
   }
diff --git a/dom/xbl/nsXBLProtoImplMethod.cpp b/dom/xbl/nsXBLProtoImplMethod.cpp
index 5e6441769738..0ab6be99264d 100644
--- a/dom/xbl/nsXBLProtoImplMethod.cpp
+++ b/dom/xbl/nsXBLProtoImplMethod.cpp
@@ -50,8 +50,6 @@ nsXBLProtoImplMethod::AppendBodyText(const nsAString& aText)
   nsXBLUncompiledMethod* uncompiledMethod = GetUncompiledMethod();
   if (!uncompiledMethod) {
     uncompiledMethod = new nsXBLUncompiledMethod();
-    if (!uncompiledMethod)
-      return;
     SetUncompiledMethod(uncompiledMethod);
   }
 
@@ -72,8 +70,6 @@ nsXBLProtoImplMethod::AddParameter(const nsAString& aText)
   nsXBLUncompiledMethod* uncompiledMethod = GetUncompiledMethod();
   if (!uncompiledMethod) {
     uncompiledMethod = new nsXBLUncompiledMethod();
-    if (!uncompiledMethod)
-      return;
     SetUncompiledMethod(uncompiledMethod);
   }
 
@@ -89,8 +85,6 @@ nsXBLProtoImplMethod::SetLineNumber(uint32_t aLineNumber)
   nsXBLUncompiledMethod* uncompiledMethod = GetUncompiledMethod();
   if (!uncompiledMethod) {
     uncompiledMethod = new nsXBLUncompiledMethod();
-    if (!uncompiledMethod)
-      return;
     SetUncompiledMethod(uncompiledMethod);
   }
 
@@ -168,8 +162,6 @@ nsXBLProtoImplMethod::CompileMember(AutoJSAPI& jsapi, const nsString& aClassStr,
   char** args = nullptr;
   if (paramCount > 0) {
     args = new char*[paramCount];
-    if (!args)
-      return NS_ERROR_OUT_OF_MEMORY;
 
     // Add our parameters to our args array.
     int32_t argPos = 0;
diff --git a/dom/xbl/nsXBLProtoImplMethod.h b/dom/xbl/nsXBLProtoImplMethod.h
index ff26c453a872..0afffcb2c382 100644
--- a/dom/xbl/nsXBLProtoImplMethod.h
+++ b/dom/xbl/nsXBLProtoImplMethod.h
@@ -65,8 +65,6 @@ struct nsXBLUncompiledMethod {
 
   void AddParameter(const nsAString& aText) {
     nsXBLParameter* param = new nsXBLParameter(aText);
-    if (!param)
-      return;
     if (!mParameters)
       mParameters = param;
     else
diff --git a/dom/xbl/nsXBLResourceLoader.cpp b/dom/xbl/nsXBLResourceLoader.cpp
index 8a9bae9f7546..96e397d0db19 100644
--- a/dom/xbl/nsXBLResourceLoader.cpp
+++ b/dom/xbl/nsXBLResourceLoader.cpp
@@ -197,9 +197,6 @@ void
 nsXBLResourceLoader::AddResource(nsIAtom* aResourceType, const nsAString& aSrc)
 {
   nsXBLResource* res = new nsXBLResource(aResourceType, aSrc);
-  if (!res)
-    return;
-
   if (!mResourceList)
     mResourceList = res;
   else