--- a/dom/base/nsINode.cpp
+++ b/dom/base/nsINode.cpp
@@ -1279,18 +1279,18 @@ nsINode::RemoveEventListener(const nsASt
   return NS_OK;
 }
 
 NS_IMPL_REMOVE_SYSTEM_EVENT_LISTENER(nsINode)
 
 nsresult
 nsINode::GetEventTargetParent(EventChainPreVisitor& aVisitor)
 {
-  // This is only here so that we can use the NS_DECL_NSIDOMTARGET macro
-  NS_ABORT();
+  MOZ_ASSERT_UNREACHABLE("GetEventTargetParent is only here so that we can "
+                         "use the NS_DECL_NSIDOMTARGET macro");
   return NS_ERROR_NOT_IMPLEMENTED;
 }
 
 void
 nsINode::GetBoxQuads(const BoxQuadOptions& aOptions,
                      nsTArray<RefPtr<DOMQuad> >& aResult,
                      CallerType aCallerType,
                      mozilla::ErrorResult& aRv)

--- a/dom/ipc/TabChild.cpp
+++ b/dom/ipc/TabChild.cpp
@@ -3477,17 +3477,17 @@ TabChild::RecvSetWidgetNativeData(const 
 }
 
 mozilla::plugins::PPluginWidgetChild*
 TabChild::AllocPPluginWidgetChild()
 {
 #ifdef XP_WIN
   return new mozilla::plugins::PluginWidgetChild();
 #else
-  MOZ_ASSERT_UNREACHABLE();
+  MOZ_ASSERT_UNREACHABLE("AllocPPluginWidgetChild only supports Windows");
   return nullptr;
 #endif
 }
 
 bool
 TabChild::DeallocPPluginWidgetChild(mozilla::plugins::PPluginWidgetChild* aActor)
 {
   delete aActor;

--- a/dom/ipc/TabParent.cpp
+++ b/dom/ipc/TabParent.cpp
@@ -3134,17 +3134,17 @@ TabParent::RecvRemoteIsReadyToHandleInpu
 }
 
 mozilla::plugins::PPluginWidgetParent*
 TabParent::AllocPPluginWidgetParent()
 {
 #ifdef XP_WIN
   return new mozilla::plugins::PluginWidgetParent();
 #else
-  MOZ_ASSERT_UNREACHABLE();
+  MOZ_ASSERT_UNREACHABLE("AllocPPluginWidgetParent only supports Windows");
   return nullptr;
 #endif
 }
 
 bool
 TabParent::DeallocPPluginWidgetParent(mozilla::plugins::PPluginWidgetParent* aActor)
 {
   delete aActor;

--- a/gfx/gl/GLContextProviderGLX.cpp
+++ b/gfx/gl/GLContextProviderGLX.cpp
@@ -469,17 +469,17 @@ GLXLibrary::AfterGLXCall() const
             char buffer[2048];
             XGetErrorText(DefaultXDisplay(), sErrorEvent.mError.error_code, buffer, sizeof(buffer));
             printf_stderr("X ERROR: %s (%i) - Request: %i.%i, Serial: %lu",
                           buffer,
                           sErrorEvent.mError.error_code,
                           sErrorEvent.mError.request_code,
                           sErrorEvent.mError.minor_code,
                           sErrorEvent.mError.serial);
-            NS_ABORT();
+            MOZ_ASSERT_UNREACHABLE("AfterGLXCall sErrorEvent");
         }
         XSetErrorHandler(sOldErrorHandler);
     }
 }
 
 already_AddRefed<GLContextGLX>
 GLContextGLX::CreateGLContext(CreateContextFlags flags, const SurfaceCaps& caps,
                               bool isOffscreen, Display* display, GLXDrawable drawable,
@@ -1082,9 +1082,8 @@ GLContextProviderGLX::GetGlobalContext()
 
 /*static*/ void
 GLContextProviderGLX::Shutdown()
 {
 }
 
 } /* namespace gl */
 } /* namespace mozilla */
-

--- a/gfx/layers/SyncObject.cpp
+++ b/gfx/layers/SyncObject.cpp
@@ -36,15 +36,15 @@ SyncObjectClient::CreateSyncObjectClient
 {
   if (!aHandle) {
     return nullptr;
   }
 
 #ifdef XP_WIN
   return MakeAndAddRef<SyncObjectD3D11Client>(aHandle, aDevice);
 #else
-  MOZ_ASSERT_UNREACHABLE();
+  MOZ_ASSERT_UNREACHABLE("CreateSyncObjectClient only supports Windows");
   return nullptr;
 #endif
 }
 
 } // namespace layers
 } // namespace mozilla

--- a/layout/forms/nsListControlFrame.cpp
+++ b/layout/forms/nsListControlFrame.cpp
@@ -2562,11 +2562,11 @@ nsListEventListener::HandleEvent(nsIDOME
     return mFrame->nsListControlFrame::MouseUp(aEvent);
   }
   if (eventType.EqualsLiteral("mousemove")) {
     // I don't think we want to honor defaultPrevented on mousemove
     // in general, and it would only prevent highlighting here.
     return mFrame->nsListControlFrame::MouseMove(aEvent);
   }
 
-  NS_ABORT();
+  MOZ_ASSERT_UNREACHABLE("Unexpected eventType");
   return NS_OK;
 }

--- a/layout/mathml/nsMathMLmactionFrame.cpp
+++ b/layout/mathml/nsMathMLmactionFrame.cpp
@@ -269,17 +269,17 @@ nsMathMLmactionFrame::MouseListener::Han
   }
   else if (eventType.EqualsLiteral("click")) {
     mOwner->MouseClick();
   }
   else if (eventType.EqualsLiteral("mouseout")) {
     mOwner->MouseOut();
   }
   else {
-    NS_ABORT();
+    MOZ_ASSERT_UNREACHABLE("Unexpected eventType");
   }
 
   return NS_OK;
 }
 
 void
 nsMathMLmactionFrame::MouseOver()
 {

--- a/layout/xul/nsButtonBoxFrame.cpp
+++ b/layout/xul/nsButtonBoxFrame.cpp
@@ -37,18 +37,17 @@ nsButtonBoxFrame::nsButtonBoxListener::H
   nsAutoString eventType;
   aEvent->GetType(eventType);
 
   if (eventType.EqualsLiteral("blur")) {
     mButtonBoxFrame->Blurred();
     return NS_OK;
   }
 
-  NS_ABORT();
-
+  MOZ_ASSERT_UNREACHABLE("Unexpected eventType");
   return NS_OK;
 }
 
 //
 // NS_NewXULButtonFrame
 //
 // Creates a new Button frame and returns it
 //

--- a/layout/xul/nsMenuBarListener.cpp
+++ b/layout/xul/nsMenuBarListener.cpp
@@ -539,12 +539,11 @@ nsMenuBarListener::HandleEvent(nsIDOMEve
   }
   if (eventType.EqualsLiteral("mousedown")) {
     return MouseDown(aEvent);
   }
   if (eventType.EqualsLiteral("MozDOMFullscreen:Entered")) {
     return Fullscreen(aEvent);
   }
 
-  NS_ABORT();
-
+  MOZ_ASSERT_UNREACHABLE("Unexpected eventType");
   return NS_OK;
 }

--- a/layout/xul/nsSplitterFrame.cpp
+++ b/layout/xul/nsSplitterFrame.cpp
@@ -584,17 +584,17 @@ nsSplitterFrameInner::HandleEvent(nsIDOM
   if (eventType.EqualsLiteral("mouseup"))
     return MouseUp(aEvent);
   if (eventType.EqualsLiteral("mousedown"))
     return MouseDown(aEvent);
   if (eventType.EqualsLiteral("mousemove") ||
       eventType.EqualsLiteral("mouseout"))
     return MouseMove(aEvent);
 
-  NS_ABORT();
+  MOZ_ASSERT_UNREACHABLE("Unexpected eventType");
   return NS_OK;
 }
 
 nsresult
 nsSplitterFrameInner::MouseUp(nsIDOMEvent* aMouseEvent)
 {
   NS_ENSURE_TRUE(mOuter, NS_OK);
   mPressed = false;

--- a/layout/xul/nsXULPopupManager.cpp
+++ b/layout/xul/nsXULPopupManager.cpp
@@ -2607,18 +2607,17 @@ nsXULPopupManager::HandleEvent(nsIDOMEve
   }
   if (eventType.EqualsLiteral("keydown")) {
     return KeyDown(keyEvent);
   }
   if (eventType.EqualsLiteral("keypress")) {
     return KeyPress(keyEvent);
   }
 
-  NS_ABORT();
-
+  MOZ_ASSERT_UNREACHABLE("Unexpected eventType");
   return NS_OK;
 }
 
 nsresult
 nsXULPopupManager::UpdateIgnoreKeys(bool aIgnoreKeys)
 {
   nsMenuChainItem* item = GetTopVisibleMenu();
   if (item) {

--- a/widget/gtk/nsWindow.cpp
+++ b/widget/gtk/nsWindow.cpp
@@ -3837,20 +3837,21 @@ nsWindow::Create(nsIWidget* aParent,
 
               gdk_window_input_shape_combine_region(mGdkWindow, region, 0, 0);
               cairo_region_destroy(region);
 #endif
             }
         }
     }
         break;
+
     case eWindowType_plugin:
     case eWindowType_plugin_ipc_chrome:
     case eWindowType_plugin_ipc_content:
-        MOZ_ASSERT_UNREACHABLE();
+        MOZ_ASSERT_UNREACHABLE("Unexpected eWindowType_plugin*");
         return NS_ERROR_FAILURE;
 
     case eWindowType_child: {
         if (parentMozContainer) {
             mGdkWindow = CreateGdkWindow(parentGdkWindow, parentMozContainer);
             mHasMappedToplevel = parentnsWindow->mHasMappedToplevel;
         }
         else if (parentGtkContainer) {

--- a/xpcom/base/nsDebug.h
+++ b/xpcom/base/nsDebug.h
@@ -158,31 +158,16 @@ inline void MOZ_PretendNoReturn()
 #ifdef DEBUG
 #define NS_WARNING(str)                                       \
   NS_DebugBreak(NS_DEBUG_WARNING, str, nullptr, __FILE__, __LINE__)
 #else
 #define NS_WARNING(str)                do { /* nothing */ } while(0)
 #endif
 
 /**
- * Trigger an debug-only abort.
- *
- * @see MOZ_RELEASE_ASSERT or MOZ_CRASH for release-mode asserts.
- */
-#ifdef DEBUG
-#define NS_ABORT()                                            \
-  do {                                                        \
-    NS_DebugBreak(NS_DEBUG_ABORT, nullptr, nullptr, __FILE__, __LINE__); \
-    MOZ_PretendNoReturn();                                    \
-  } while(0)
-#else
-#define NS_ABORT()                     do { /* nothing */ } while(0)
-#endif
-
-/**
  * Trigger a debugger breakpoint, only in debug builds.
  */
 #ifdef DEBUG
 #define NS_BREAK()                                            \
   do {                                                        \
     NS_DebugBreak(NS_DEBUG_BREAK, nullptr, nullptr, __FILE__, __LINE__); \
     MOZ_PretendNoReturn();                                    \
   } while(0)