diff --git a/layout/base/nsCSSFrameConstructor.cpp b/layout/base/nsCSSFrameConstructor.cpp
index 01bdb1b4dab..c91c49b81e1 100644
--- a/layout/base/nsCSSFrameConstructor.cpp
+++ b/layout/base/nsCSSFrameConstructor.cpp
@@ -1600,8 +1600,6 @@ nsCSSFrameConstructor::CreateGeneratedContent(nsFrameConstructorState& aState,
       nsCounterUseNode* node =
         new nsCounterUseNode(counters, aContentIndex,
                              type == eStyleContentType_Counters);
-      if (!node)
-        return nsnull;
 
       nsGenConInitializer* initializer =
         new nsGenConInitializer(node, counterList,
@@ -1621,8 +1619,6 @@ nsCSSFrameConstructor::CreateGeneratedContent(nsFrameConstructorState& aState,
     {
       nsQuoteNode* node =
         new nsQuoteNode(type, aContentIndex);
-      if (!node)
-        return nsnull;
 
       nsGenConInitializer* initializer =
         new nsGenConInitializer(node, &mQuoteList,
@@ -5072,9 +5068,7 @@ nsCSSFrameConstructor::AddFrameConstructionItemsInternal(nsFrameConstructorState
     PRBool resolveStyle;
 
     nsAutoPtr<PendingBinding> newPendingBinding(new PendingBinding());
-    if (!newPendingBinding) {
-      return;
-    }
+
     nsresult rv = xblService->LoadBindings(aContent, display->mBinding->GetURI(),
                                            display->mBinding->mOriginPrincipal,
                                            PR_FALSE,
@@ -9405,10 +9399,6 @@ nsCSSFrameConstructor::CreateNeededTablePseudos(nsFrameConstructorState& aState,
                                 wrapperStyle.forget(),
                                 PR_TRUE);
 
-    if (!newItem) {
-      return NS_ERROR_OUT_OF_MEMORY;
-    }
-
     // Here we're cheating a tad... technically, table-internal items should be
     // inline if aParentFrame is inline, but they'll get wrapped in an
     // inline-table in the end, so it'll all work out.  In any case, arguably
diff --git a/layout/base/nsCSSFrameConstructor.h b/layout/base/nsCSSFrameConstructor.h
index c16c7e86de5..7a66e40e6b4 100644
--- a/layout/base/nsCSSFrameConstructor.h
+++ b/layout/base/nsCSSFrameConstructor.h
@@ -856,14 +856,9 @@ private:
         new FrameConstructionItem(aFCData, aContent, aTag, aNameSpaceID,
                                   aPendingBinding, aStyleContext,
                                   aSuppressWhiteSpaceOptimizations);
-      if (item) {
-        PR_APPEND_LINK(item, &mItems);
-        ++mItemCount;
-        ++mDesiredParentCounts[item->DesiredParentType()];
-      } else {
-        // Clean up the style context
-        nsRefPtr<nsStyleContext> sc(aStyleContext);
-      }
+      PR_APPEND_LINK(item, &mItems);
+      ++mItemCount;
+      ++mDesiredParentCounts[item->DesiredParentType()];
       return item;
     }
 
diff --git a/layout/base/nsCSSRendering.cpp b/layout/base/nsCSSRendering.cpp
index 23cab9e52ef..301f4f92e72 100644
--- a/layout/base/nsCSSRendering.cpp
+++ b/layout/base/nsCSSRendering.cpp
@@ -2121,7 +2121,7 @@ nsCSSRendering::PaintGradient(nsPresContext* aPresContext,
     }
     gradientPattern = new gfxPattern(lineStart.x, lineStart.y, innerRadius,
                                      lineStart.x, lineStart.y, outerRadius);
-    if (gradientPattern && radiusX != radiusY) {
+    if (radiusX != radiusY) {
       // Stretch the circles into ellipses vertically by setting a transform
       // in the pattern.
       // Recall that this is the transform from user space to pattern space.
@@ -2134,7 +2134,7 @@ nsCSSRendering::PaintGradient(nsPresContext* aPresContext,
       gradientPattern->SetMatrix(matrix);
     }
   }
-  if (!gradientPattern || gradientPattern->CairoStatus())
+  if (gradientPattern->CairoStatus())
     return;
 
   // Now set normalized color stops in pattern.
diff --git a/layout/base/nsCounterManager.cpp b/layout/base/nsCounterManager.cpp
index 340075be111..9233376e57a 100644
--- a/layout/base/nsCounterManager.cpp
+++ b/layout/base/nsCounterManager.cpp
@@ -244,8 +244,6 @@ nsCounterManager::AddResetOrIncrement(nsIFrame *aFrame, PRInt32 aIndex,
 {
     nsCounterChangeNode *node =
         new nsCounterChangeNode(aFrame, aType, aCounterData->mValue, aIndex);
-    if (!node)
-        return PR_FALSE;
 
     nsCounterList *counterList = CounterListFor(aCounterData->mCounter);
     if (!counterList) {
@@ -277,8 +275,6 @@ nsCounterManager::CounterListFor(const nsSubstring& aCounterName)
     nsCounterList *counterList;
     if (!mNames.Get(aCounterName, &counterList)) {
         counterList = new nsCounterList();
-        if (!counterList)
-            return nsnull;
         if (!mNames.Put(aCounterName, counterList)) {
             delete counterList;
             return nsnull;
diff --git a/layout/base/nsDisplayList.cpp b/layout/base/nsDisplayList.cpp
index b843c416600..81e312727bf 100644
--- a/layout/base/nsDisplayList.cpp
+++ b/layout/base/nsDisplayList.cpp
@@ -574,8 +574,6 @@ void nsDisplayList::PaintForFrame(nsDisplayListBuilder* aBuilder,
       return;
     }
     layerManager = new BasicLayerManager();
-    if (!layerManager)
-      return;
   }
 
   if (aFlags & PAINT_FLUSH_LAYERS) {
diff --git a/layout/base/nsDocumentViewer.cpp b/layout/base/nsDocumentViewer.cpp
index 8016ff1607f..376baac8d56 100644
--- a/layout/base/nsDocumentViewer.cpp
+++ b/layout/base/nsDocumentViewer.cpp
@@ -545,9 +545,6 @@ nsresult
 NS_NewDocumentViewer(nsIDocumentViewer** aResult)
 {
   *aResult = new DocumentViewerImpl();
-  if (!*aResult) {
-    return NS_ERROR_OUT_OF_MEMORY;
-  }
 
   NS_ADDREF(*aResult);
 
@@ -800,7 +797,6 @@ DocumentViewerImpl::InitPresentationStuff(PRBool aDoInitialReflow)
   if (!mSelectionListener) {
     nsDocViewerSelectionListener *selectionListener =
       new nsDocViewerSelectionListener();
-    NS_ENSURE_TRUE(selectionListener, NS_ERROR_OUT_OF_MEMORY);
 
     selectionListener->Init(this);
 
@@ -825,7 +821,6 @@ DocumentViewerImpl::InitPresentationStuff(PRBool aDoInitialReflow)
   // now register ourselves as a focus listener, so that we get called
   // when the focus changes in the window
   nsDocViewerFocusListener *focusListener = new nsDocViewerFocusListener();
-  NS_ENSURE_TRUE(focusListener, NS_ERROR_OUT_OF_MEMORY);
 
   focusListener->Init(this);
 
@@ -2180,9 +2175,6 @@ DocumentViewerImpl::CreateStyleSet(nsIDocument* aDocument,
   // this should eventually get expanded to allow for creating
   // different sets for different media
   nsStyleSet *styleSet = new nsStyleSet();
-  if (!styleSet) {
-    return NS_ERROR_OUT_OF_MEMORY;
-  }
 
   styleSet->BeginUpdate();
   
@@ -3684,7 +3676,6 @@ DocumentViewerImpl::Print(nsIPrintSettings*       aPrintSettings,
 
   if (!mPrintEngine) {
     mPrintEngine = new nsPrintEngine();
-    NS_ENSURE_TRUE(mPrintEngine, NS_ERROR_OUT_OF_MEMORY);
 
     rv = mPrintEngine->Initialize(this, mContainer, mDocument, 
                                   float(mDeviceContext->AppUnitsPerCSSInch()) /
@@ -3751,7 +3742,6 @@ DocumentViewerImpl::PrintPreview(nsIPrintSettings* aPrintSettings,
   nsPrintEventDispatcher beforeAndAfterPrint(doc);
   if (!mPrintEngine) {
     mPrintEngine = new nsPrintEngine();
-    NS_ENSURE_TRUE(mPrintEngine, NS_ERROR_OUT_OF_MEMORY);
 
     rv = mPrintEngine->Initialize(this, mContainer, doc,
                                   float(mDeviceContext->AppUnitsPerCSSInch()) /
diff --git a/layout/base/nsFrameManager.cpp b/layout/base/nsFrameManager.cpp
index 7859cbc1468..58593686bed 100644
--- a/layout/base/nsFrameManager.cpp
+++ b/layout/base/nsFrameManager.cpp
@@ -380,14 +380,12 @@ nsFrameManager::SetUndisplayedContent(nsIContent* aContent,
   if (! mUndisplayedMap) {
     mUndisplayedMap = new UndisplayedMap;
   }
-  if (mUndisplayedMap) {
-    nsIContent* parent = aContent->GetParent();
-    NS_ASSERTION(parent || (mPresShell && mPresShell->GetDocument() &&
-                 mPresShell->GetDocument()->GetRootElement() == aContent),
-                 "undisplayed content must have a parent, unless it's the root "
-                 "element");
-    mUndisplayedMap->AddNodeFor(parent, aContent, aStyleContext);
-  }
+  nsIContent* parent = aContent->GetParent();
+  NS_ASSERTION(parent || (mPresShell && mPresShell->GetDocument() &&
+               mPresShell->GetDocument()->GetRootElement() == aContent),
+               "undisplayed content must have a parent, unless it's the root "
+               "element");
+  mUndisplayedMap->AddNodeFor(parent, aContent, aStyleContext);
 }
 
 void
@@ -1900,9 +1898,6 @@ nsFrameManagerBase::UndisplayedMap::AddNodeFor(nsIContent* aParentContent,
                                                nsStyleContext* aStyle)
 {
   UndisplayedNode*  node = new UndisplayedNode(aChild, aStyle);
-  if (! node) {
-    return NS_ERROR_OUT_OF_MEMORY;
-  }
 
   AppendNodeFor(node, aParentContent);
   return NS_OK;
diff --git a/layout/base/nsFrameTraversal.cpp b/layout/base/nsFrameTraversal.cpp
index 7b18636e76f..76c3793feae 100644
--- a/layout/base/nsFrameTraversal.cpp
+++ b/layout/base/nsFrameTraversal.cpp
@@ -151,8 +151,6 @@ nsresult NS_CreateFrameTraversal(nsIFrameTraversal** aResult)
   *aResult = nsnull;
 
   nsCOMPtr<nsIFrameTraversal> t(new nsFrameTraversal());
-  if (!t)
-    return NS_ERROR_OUT_OF_MEMORY;
 
   *aResult = t;
   NS_ADDREF(*aResult);
@@ -179,10 +177,7 @@ NS_NewFrameTraversal(nsIFrameEnumerator **aEnumerator,
     trav = new nsFrameIterator(aPresContext, aStart, aType,
                                aLockInScrollView, aFollowOOFs);
   }
-  if (!trav)
-    return NS_ERROR_OUT_OF_MEMORY;
-  *aEnumerator = trav;
-  NS_ADDREF(trav);
+  trav.forget(aEnumerator);
   return NS_OK;
 }
 
diff --git a/layout/base/nsLayoutDebugger.cpp b/layout/base/nsLayoutDebugger.cpp
index de70226f342..9b160cd38a6 100644
--- a/layout/base/nsLayoutDebugger.cpp
+++ b/layout/base/nsLayoutDebugger.cpp
@@ -84,9 +84,6 @@ NS_NewLayoutDebugger(nsILayoutDebugger** aResult)
     return NS_ERROR_NULL_POINTER;
   }
   nsLayoutDebugger* it = new nsLayoutDebugger();
-  if (!it) {
-    return NS_ERROR_OUT_OF_MEMORY;
-  }
   return it->QueryInterface(NS_GET_IID(nsILayoutDebugger), (void**)aResult);
 }
 
diff --git a/layout/base/nsLayoutHistoryState.cpp b/layout/base/nsLayoutHistoryState.cpp
index 5c5a28710d6..894c3c6fcdf 100644
--- a/layout/base/nsLayoutHistoryState.cpp
+++ b/layout/base/nsLayoutHistoryState.cpp
@@ -77,8 +77,6 @@ NS_NewLayoutHistoryState(nsILayoutHistoryState** aState)
 
   *aState = nsnull;
   state = new nsLayoutHistoryState();
-  if (!state)
-    return NS_ERROR_OUT_OF_MEMORY;
 
   NS_ADDREF(state);
   nsresult rv = state->Init();
diff --git a/layout/base/nsLayoutUtils.cpp b/layout/base/nsLayoutUtils.cpp
index b7581846283..283033ced56 100644
--- a/layout/base/nsLayoutUtils.cpp
+++ b/layout/base/nsLayoutUtils.cpp
@@ -1811,10 +1811,6 @@ nsLayoutUtils::RectListBuilder::RectListBuilder(nsClientRectList* aList)
 
 void nsLayoutUtils::RectListBuilder::AddRect(const nsRect& aRect) {
   nsRefPtr<nsClientRect> rect = new nsClientRect();
-  if (!rect) {
-    mRV = NS_ERROR_OUT_OF_MEMORY;
-    return;
-  }
 
   rect->SetLayoutRect(aRect);
   mRectList->Append(rect);
@@ -3876,12 +3872,8 @@ nsLayoutUtils::SurfaceFromElement(nsIDOMElement *aElement,
     if (wantImageSurface && surf->GetType() != gfxASurface::SurfaceTypeImage) {
       nsRefPtr<gfxImageSurface> imgSurf =
         new gfxImageSurface(size, gfxASurface::ImageFormatARGB32);
-      if (!imgSurf)
-        return result;
 
       nsRefPtr<gfxContext> ctx = new gfxContext(imgSurf);
-      if (!ctx)
-        return result;
       ctx->SetOperator(gfxContext::OPERATOR_SOURCE);
       ctx->DrawSurface(surf, size);
       surf = imgSurf;
diff --git a/layout/base/nsPresContext.cpp b/layout/base/nsPresContext.cpp
index 22936eb9603..1b5b6e79163 100644
--- a/layout/base/nsPresContext.cpp
+++ b/layout/base/nsPresContext.cpp
@@ -912,18 +912,11 @@ nsPresContext::Init(nsDeviceContext* aDeviceContext)
   }
 
   mEventManager = new nsEventStateManager();
-  if (!mEventManager)
-    return NS_ERROR_OUT_OF_MEMORY;
-
   NS_ADDREF(mEventManager);
 
   mTransitionManager = new nsTransitionManager(this);
-  if (!mTransitionManager)
-    return NS_ERROR_OUT_OF_MEMORY;
 
   mAnimationManager = new nsAnimationManager(this);
-  if (!mAnimationManager)
-    return NS_ERROR_OUT_OF_MEMORY;
 
   if (mDocument->GetDisplayDocument()) {
     NS_ASSERTION(mDocument->GetDisplayDocument()->GetShell() &&
@@ -959,8 +952,6 @@ nsPresContext::Init(nsDeviceContext* aDeviceContext)
 
     if (!mRefreshDriver) {
       mRefreshDriver = new nsRefreshDriver(this);
-      if (!mRefreshDriver)
-        return NS_ERROR_OUT_OF_MEMORY;
     }
   }
 
diff --git a/layout/base/nsPresShell.cpp b/layout/base/nsPresShell.cpp
index 448a891c7c3..f6fec5924de 100644
--- a/layout/base/nsPresShell.cpp
+++ b/layout/base/nsPresShell.cpp
@@ -1244,10 +1244,8 @@ protected:
                                 aEvent->widget,
                                 aEvent->reason,
                                 aEvent->context);
-      if (mEvent) {
-        Init(aEvent);
-        static_cast<nsMouseEvent*>(mEvent)->clickCount = aEvent->clickCount;
-      }
+      Init(aEvent);
+      static_cast<nsMouseEvent*>(mEvent)->clickCount = aEvent->clickCount;
     }
 
     virtual ~nsDelayedMouseEvent()
@@ -1264,14 +1262,12 @@ protected:
       mEvent = new nsKeyEvent(NS_IS_TRUSTED_EVENT(aEvent),
                               aEvent->message,
                               aEvent->widget);
-      if (mEvent) {
-        Init(aEvent);
-        static_cast<nsKeyEvent*>(mEvent)->keyCode = aEvent->keyCode;
-        static_cast<nsKeyEvent*>(mEvent)->charCode = aEvent->charCode;
-        static_cast<nsKeyEvent*>(mEvent)->alternativeCharCodes =
-          aEvent->alternativeCharCodes;
-        static_cast<nsKeyEvent*>(mEvent)->isChar = aEvent->isChar;
-      }
+      Init(aEvent);
+      static_cast<nsKeyEvent*>(mEvent)->keyCode = aEvent->keyCode;
+      static_cast<nsKeyEvent*>(mEvent)->charCode = aEvent->charCode;
+      static_cast<nsKeyEvent*>(mEvent)->alternativeCharCodes =
+        aEvent->alternativeCharCodes;
+      static_cast<nsKeyEvent*>(mEvent)->isChar = aEvent->isChar;
     }
 
     virtual ~nsDelayedKeyEvent()
@@ -1664,8 +1660,6 @@ NS_NewPresShell(nsIPresShell** aInstancePtrResult)
     return NS_ERROR_NULL_POINTER;
 
   *aInstancePtrResult = new PresShell();
-  if (!*aInstancePtrResult)
-    return NS_ERROR_OUT_OF_MEMORY;
 
   NS_ADDREF(*aInstancePtrResult);
   return NS_OK;
@@ -1801,7 +1795,6 @@ PresShell::Init(nsIDocument* aDocument,
 
   // Create our frame constructor.
   mFrameConstructor = new nsCSSFrameConstructor(mDocument, this);
-  NS_ENSURE_TRUE(mFrameConstructor, NS_ERROR_OUT_OF_MEMORY);
 
   // The document viewer owns both view manager and pres shell.
   mViewManager->SetViewObserver(this);
@@ -5486,8 +5479,6 @@ PresShell::CreateRangePaintInfo(nsIDOMRange* aRange,
     return nsnull;
 
   info = new RangePaintInfo(range, ancestorFrame);
-  if (!info)
-    return nsnull;
 
   nsRect ancestorRect = ancestorFrame->GetVisualOverflowRect();
 
@@ -5589,7 +5580,7 @@ PresShell::PaintRangePaintInfo(nsTArray<nsAutoPtr<RangePaintInfo> >* aItems,
   gfxImageSurface* surface =
     new gfxImageSurface(gfxIntSize(pixelArea.width, pixelArea.height),
                         gfxImageSurface::ImageFormatARGB32);
-  if (!surface || surface->CairoStatus()) {
+  if (surface->CairoStatus()) {
     delete surface;
     return nsnull;
   }
@@ -6565,7 +6556,7 @@ PresShell::HandleEvent(nsIView         *aView,
     } else if (!mNoDelayedKeyEvents) {
       nsDelayedEvent* event =
         new nsDelayedKeyEvent(static_cast<nsKeyEvent*>(aEvent));
-      if (event && !mDelayedEvents.AppendElement(event)) {
+      if (!mDelayedEvents.AppendElement(event)) {
         delete event;
       }
     }
@@ -8595,7 +8586,6 @@ DumpToPNG(nsIPresShell* shell, nsAString& name) {
   nsRefPtr<gfxImageSurface> imgSurface =
      new gfxImageSurface(gfxIntSize(width, height),
                          gfxImageSurface::ImageFormatARGB32);
-  NS_ENSURE_TRUE(imgSurface, NS_ERROR_OUT_OF_MEMORY);
 
   nsRefPtr<gfxContext> imgContext = new gfxContext(imgSurface);
 
@@ -8606,7 +8596,6 @@ DumpToPNG(nsIPresShell* shell, nsAString& name) {
   NS_ENSURE_TRUE(surface, NS_ERROR_OUT_OF_MEMORY);
 
   nsRefPtr<gfxContext> context = new gfxContext(surface);
-  NS_ENSURE_TRUE(context, NS_ERROR_OUT_OF_MEMORY);
 
   shell->RenderDocument(r, 0, NS_RGB(255, 255, 0), context);
 
@@ -8979,7 +8968,6 @@ void ReflowCountMgr::Add(const char * aName, nsIFrame * aFrame)
     ReflowCounter * counter = (ReflowCounter *)PL_HashTableLookup(mCounts, aName);
     if (counter == nsnull) {
       counter = new ReflowCounter(this);
-      NS_ASSERTION(counter != nsnull, "null ptr");
       char * name = NS_strdup(aName);
       NS_ASSERTION(name != nsnull, "null ptr");
       PL_HashTableAdd(mCounts, name, counter);
@@ -8995,7 +8983,6 @@ void ReflowCountMgr::Add(const char * aName, nsIFrame * aFrame)
     IndiReflowCounter * counter = (IndiReflowCounter *)PL_HashTableLookup(mIndiFrameCounts, key);
     if (counter == nsnull) {
       counter = new IndiReflowCounter(this);
-      NS_ASSERTION(counter != nsnull, "null ptr");
       counter->mFrame = aFrame;
       counter->mName.AssignASCII(aName);
       PL_HashTableAdd(mIndiFrameCounts, key, counter);
diff --git a/layout/base/nsStyleSheetService.cpp b/layout/base/nsStyleSheetService.cpp
index 0b62c8ec5e2..bc95d5a0707 100644
--- a/layout/base/nsStyleSheetService.cpp
+++ b/layout/base/nsStyleSheetService.cpp
@@ -169,7 +169,6 @@ nsStyleSheetService::LoadAndRegisterSheetInternal(nsIURI *aSheetURI,
   NS_ENSURE_ARG_POINTER(aSheetURI);
 
   nsRefPtr<mozilla::css::Loader> loader = new mozilla::css::Loader();
-  NS_ENSURE_TRUE(loader, NS_ERROR_OUT_OF_MEMORY);
 
   nsRefPtr<nsCSSStyleSheet> sheet;
   // Allow UA sheets, but not user sheets, to use unsafe rules