--- a/dom/html/nsTextEditorState.cpp
+++ b/dom/html/nsTextEditorState.cpp
@@ -1563,18 +1563,19 @@ nsTextEditorState::PrepareEditor(const n
       editorFlags |= nsIPlaintextEditor::eEditorReadonlyMask;
 
     // Check if the disabled attribute is set.
     // TODO: call IsDisabled() here!
     if (content->HasAttr(kNameSpaceID_None, nsGkAtoms::disabled))
       editorFlags |= nsIPlaintextEditor::eEditorDisabledMask;
 
     // Disable the selection if necessary.
-    if (editorFlags & nsIPlaintextEditor::eEditorDisabledMask)
+    if (newTextEditor->IsDisabled()) {
       mSelCon->SetDisplaySelection(nsISelectionController::SELECTION_OFF);
+    }
 
     newTextEditor->SetFlags(editorFlags);
   }
 
   if (shouldInitializeEditor) {
     // Hold on to the newly created editor
     preDestroyer.Swap(mTextEditor);
   }

--- a/editor/composer/nsComposerDocumentCommands.cpp
+++ b/editor/composer/nsComposerDocumentCommands.cpp
@@ -227,26 +227,19 @@ nsSetDocumentStateCommand::DoCommandPara
     return textEditor->ResetModificationCount();
   }
 
   if (!nsCRT::strcmp(aCommandName, "cmd_setDocumentReadOnly")) {
     NS_ENSURE_ARG_POINTER(aParams);
     bool isReadOnly;
     nsresult rvRO = aParams->GetBooleanValue(STATE_ATTRIBUTE, &isReadOnly);
     NS_ENSURE_SUCCESS(rvRO, rvRO);
-
-    uint32_t flags;
-    textEditor->GetFlags(&flags);
-    if (isReadOnly) {
-      flags |= nsIPlaintextEditor::eEditorReadonlyMask;
-    } else {
-      flags &= ~(nsIPlaintextEditor::eEditorReadonlyMask);
-    }
-
-    return textEditor->SetFlags(flags);
+    return isReadOnly ?
+      textEditor->AddFlags(nsIPlaintextEditor::eEditorReadonlyMask) :
+      textEditor->RemoveFlags(nsIPlaintextEditor::eEditorReadonlyMask);
   }
 
   if (!nsCRT::strcmp(aCommandName, "cmd_setDocumentUseCSS")) {
     NS_ENSURE_ARG_POINTER(aParams);
     HTMLEditor* htmlEditor = textEditor->AsHTMLEditor();
     if (NS_WARN_IF(!htmlEditor)) {
       return NS_ERROR_INVALID_ARG;
     }

--- a/editor/libeditor/EditorBase.cpp
+++ b/editor/libeditor/EditorBase.cpp
@@ -1330,20 +1330,19 @@ EditorBase::RemoveAttribute(Element* aEl
   RefPtr<ChangeAttributeTransaction> transaction =
     CreateTxnForRemoveAttribute(*aElement, *aAttribute);
   return DoTransaction(transaction);
 }
 
 bool
 EditorBase::OutputsMozDirty()
 {
-  // Return true for Composer (!eEditorAllowInteraction) or mail
-  // (eEditorMailMask), but false for webpages.
-  return !(mFlags & nsIPlaintextEditor::eEditorAllowInteraction) ||
-          (mFlags & nsIPlaintextEditor::eEditorMailMask);
+  // Return true for Composer (!IsInteractionAllowed()) or mail
+  // (IsMailEditor()), but false for webpages.
+  return !IsInteractionAllowed() || IsMailEditor();
 }
 
 NS_IMETHODIMP
 EditorBase::MarkNodeDirty(nsIDOMNode* aNode)
 {
   // Mark the node dirty, but not for webpages (bug 599983)
   if (!OutputsMozDirty()) {
     return NS_OK;
@@ -4999,18 +4998,17 @@ nsresult
 EditorBase::DetermineCurrentDirection()
 {
   // Get the current root direction from its frame
   nsIContent* rootElement = GetExposedRoot();
   NS_ENSURE_TRUE(rootElement, NS_ERROR_FAILURE);
 
   // If we don't have an explicit direction, determine our direction
   // from the content's direction
-  if (!(mFlags & (nsIPlaintextEditor::eEditorLeftToRight |
-                  nsIPlaintextEditor::eEditorRightToLeft))) {
+  if (!IsRightToLeft() && !IsLeftToRight()) {
     nsIFrame* frame = rootElement->GetPrimaryFrame();
     NS_ENSURE_TRUE(frame, NS_ERROR_FAILURE);
 
     // Set the flag here, to enable us to use the same code path below.
     // It will be flipped before returning from the function.
     if (frame->StyleVisibility()->mDirection == NS_STYLE_DIRECTION_RTL) {
       mFlags |= nsIPlaintextEditor::eEditorRightToLeft;
     } else {
@@ -5026,24 +5024,24 @@ EditorBase::SwitchTextDirection()
 {
   // Get the current root direction from its frame
   nsIContent* rootElement = GetExposedRoot();
 
   nsresult rv = DetermineCurrentDirection();
   NS_ENSURE_SUCCESS(rv, rv);
 
   // Apply the opposite direction
-  if (mFlags & nsIPlaintextEditor::eEditorRightToLeft) {
-    NS_ASSERTION(!(mFlags & nsIPlaintextEditor::eEditorLeftToRight),
+  if (IsRightToLeft()) {
+    NS_ASSERTION(!IsLeftToRight(),
                  "Unexpected mutually exclusive flag");
     mFlags &= ~nsIPlaintextEditor::eEditorRightToLeft;
     mFlags |= nsIPlaintextEditor::eEditorLeftToRight;
     rv = rootElement->SetAttr(kNameSpaceID_None, nsGkAtoms::dir, NS_LITERAL_STRING("ltr"), true);
-  } else if (mFlags & nsIPlaintextEditor::eEditorLeftToRight) {
-    NS_ASSERTION(!(mFlags & nsIPlaintextEditor::eEditorRightToLeft),
+  } else if (IsLeftToRight()) {
+    NS_ASSERTION(!IsRightToLeft(),
                  "Unexpected mutually exclusive flag");
     mFlags |= nsIPlaintextEditor::eEditorRightToLeft;
     mFlags &= ~nsIPlaintextEditor::eEditorLeftToRight;
     rv = rootElement->SetAttr(kNameSpaceID_None, nsGkAtoms::dir, NS_LITERAL_STRING("rtl"), true);
   }
 
   if (NS_SUCCEEDED(rv)) {
     FireInputEvent();
@@ -5058,24 +5056,24 @@ EditorBase::SwitchTextDirectionTo(uint32
   // Get the current root direction from its frame
   nsIContent* rootElement = GetExposedRoot();
 
   nsresult rv = DetermineCurrentDirection();
   NS_ENSURE_SUCCESS_VOID(rv);
 
   // Apply the requested direction
   if (aDirection == nsIPlaintextEditor::eEditorLeftToRight &&
-      (mFlags & nsIPlaintextEditor::eEditorRightToLeft)) {
+      IsRightToLeft()) {
     NS_ASSERTION(!(mFlags & nsIPlaintextEditor::eEditorLeftToRight),
                  "Unexpected mutually exclusive flag");
     mFlags &= ~nsIPlaintextEditor::eEditorRightToLeft;
     mFlags |= nsIPlaintextEditor::eEditorLeftToRight;
     rv = rootElement->SetAttr(kNameSpaceID_None, nsGkAtoms::dir, NS_LITERAL_STRING("ltr"), true);
   } else if (aDirection == nsIPlaintextEditor::eEditorRightToLeft &&
-             (mFlags & nsIPlaintextEditor::eEditorLeftToRight)) {
+             IsLeftToRight()) {
     NS_ASSERTION(!(mFlags & nsIPlaintextEditor::eEditorRightToLeft),
                  "Unexpected mutually exclusive flag");
     mFlags |= nsIPlaintextEditor::eEditorRightToLeft;
     mFlags &= ~nsIPlaintextEditor::eEditorLeftToRight;
     rv = rootElement->SetAttr(kNameSpaceID_None, nsGkAtoms::dir, NS_LITERAL_STRING("rtl"), true);
   }
 
   if (NS_SUCCEEDED(rv)) {

--- a/layout/forms/nsTextControlFrame.cpp
+++ b/layout/forms/nsTextControlFrame.cpp
@@ -1000,52 +1000,52 @@ nsTextControlFrame::AttributeChanged(int
       } else { // unset the maxLength attribute
         textEditor->SetMaxTextLength(-1);
       }
     }
     return NS_OK;
   }
 
   if (nsGkAtoms::readonly == aAttribute) {
-    uint32_t flags;
-    textEditor->GetFlags(&flags);
     if (AttributeExists(nsGkAtoms::readonly)) { // set readonly
-      flags |= nsIPlaintextEditor::eEditorReadonlyMask;
       if (nsContentUtils::IsFocusedContent(mContent)) {
         selCon->SetCaretEnabled(false);
       }
+      textEditor->AddFlags(nsIPlaintextEditor::eEditorReadonlyMask);
     } else { // unset readonly
-      flags &= ~(nsIPlaintextEditor::eEditorReadonlyMask);
       if (!textEditor->IsDisabled() &&
           nsContentUtils::IsFocusedContent(mContent)) {
         selCon->SetCaretEnabled(true);
       }
+      textEditor->RemoveFlags(nsIPlaintextEditor::eEditorReadonlyMask);
     }
-    textEditor->SetFlags(flags);
     return NS_OK;
   }
 
   if (nsGkAtoms::disabled == aAttribute) {
-    uint32_t flags;
-    textEditor->GetFlags(&flags);
     int16_t displaySelection = nsISelectionController::SELECTION_OFF;
     const bool focused = nsContentUtils::IsFocusedContent(mContent);
     const bool hasAttr = AttributeExists(nsGkAtoms::disabled);
+    bool disable;
     if (hasAttr) { // set disabled
-      flags |= nsIPlaintextEditor::eEditorDisabledMask;
+      disable = true;
     } else { // unset disabled
-      flags &= ~(nsIPlaintextEditor::eEditorDisabledMask);
+      disable = false;
       displaySelection = focused ? nsISelectionController::SELECTION_ON
                                  : nsISelectionController::SELECTION_HIDDEN;
     }
     selCon->SetDisplaySelection(displaySelection);
     if (focused) {
       selCon->SetCaretEnabled(!hasAttr);
     }
-    textEditor->SetFlags(flags);
+    if (disable) {
+      textEditor->AddFlags(nsIPlaintextEditor::eEditorDisabledMask);
+    } else {
+      textEditor->RemoveFlags(nsIPlaintextEditor::eEditorDisabledMask);
+    }
     return NS_OK;
   }
 
   if (!mEditorHasBeenInitialized && nsGkAtoms::value == aAttribute) {
     UpdateValueDisplay(true);
     return NS_OK;
   }