--- a/browser/components/preferences/applications.js
+++ b/browser/components/preferences/applications.js
@@ -450,39 +450,26 @@ HandlerInfoWrapper.prototype = {
   disablePluginType: function() {
     var disabledPluginTypes = this._getDisabledPluginTypes();
 
     if (disabledPluginTypes.indexOf(this.type) == -1)
       disabledPluginTypes.push(this.type);
 
     this._prefSvc.setCharPref(PREF_DISABLED_PLUGIN_TYPES,
                               disabledPluginTypes.join(","));
-
-    // Update the category manager so existing browser windows update.
-    this._categoryMgr.deleteCategoryEntry("Gecko-Content-Viewers",
-                                          this.type,
-                                          false);
   },
 
   enablePluginType: function() {
     var disabledPluginTypes = this._getDisabledPluginTypes();
 
     var type = this.type;
     disabledPluginTypes = disabledPluginTypes.filter(function(v) v != type);
 
     this._prefSvc.setCharPref(PREF_DISABLED_PLUGIN_TYPES,
                               disabledPluginTypes.join(","));
-
-    // Update the category manager so existing browser windows update.
-    this._categoryMgr.
-      addCategoryEntry("Gecko-Content-Viewers",
-                       this.type,
-                       "@mozilla.org/content/plugin/document-loader-factory;1",
-                       false,
-                       true);
   },
 
 
   //**************************************************************************//
   // Storage
 
   store: function() {
     this._handlerSvc.store(this.wrappedHandlerInfo);

--- a/content/base/public/nsIContentUtils.h
+++ b/content/base/public/nsIContentUtils.h
@@ -32,25 +32,40 @@
  * and other provisions required by the GPL or the LGPL. If you do not delete
  * the provisions above, a recipient may use your version of this file under
  * the terms of any one of the MPL, the GPL or the LGPL.
  *
  * ***** END LICENSE BLOCK ***** */
 #ifndef nsIContentUtils_h__
 #define nsIContentUtils_h__
 
+#include "nsIDocumentLoaderFactory.h"
+#include "nsCOMPtr.h"
+
 // C4EA618E-A3D9-4524-8EEA-E92F26FC44DB
 #define NS_ICONTENTUTILS_IID \
 { 0xC4EA618E, 0xA3D9, 0x4524, \
   { 0x8E, 0xEA, 0xE9, 0x2F, 0x26, 0xFC, 0x44, 0xDB } }
 
 class nsIContentUtils : public nsISupports
 {
 public:
     NS_DECLARE_STATIC_IID_ACCESSOR(NS_ICONTENTUTILS_IID)
     NS_DECL_ISUPPORTS
 
     virtual PRBool IsSafeToRunScript();
+
+    enum ContentViewerType
+    {
+        TYPE_UNSUPPORTED,
+        TYPE_CONTENT,
+        TYPE_PLUGIN,
+        TYPE_UNKNOWN
+    };
+
+    virtual already_AddRefed<nsIDocumentLoaderFactory>
+    FindInternalContentViewer(const char* aType,
+                              ContentViewerType* aLoaderType = NULL);
 };
 
 NS_DEFINE_STATIC_IID_ACCESSOR(nsIContentUtils, NS_ICONTENTUTILS_IID)
 
 #endif /* nsIContentUtils_h__ */

--- a/content/base/src/nsContentUtils.cpp
+++ b/content/base/src/nsContentUtils.cpp
@@ -175,16 +175,18 @@ static NS_DEFINE_CID(kXTFServiceCID, NS_
 #include "nsHtml5Module.h"
 #include "nsPresContext.h"
 #include "nsLayoutStatics.h"
 #include "nsLayoutUtils.h"
 #include "nsFrameManager.h"
 #include "BasicLayers.h"
 #include "nsFocusManager.h"
 #include "nsTextEditorState.h"
+#include "nsIPluginHost.h"
+#include "nsICategoryManager.h"
 
 #ifdef IBMBIDI
 #include "nsIBidiKeyboard.h"
 #endif
 #include "nsCycleCollectionParticipant.h"
 
 // for ReportToConsole
 #include "nsIStringBundle.h"
@@ -198,16 +200,17 @@ static NS_DEFINE_CID(kXTFServiceCID, NS_
 #include "jsdate.h"
 #include "jsregexp.h"
 #include "jstypedarray.h"
 #include "xpcprivate.h"
 #include "nsScriptSecurityManager.h"
 #include "nsIChannelPolicy.h"
 #include "nsChannelPolicy.h"
 #include "nsIContentSecurityPolicy.h"
+#include "nsContentDLF.h"
 
 using namespace mozilla::dom;
 
 const char kLoadAsData[] = "loadAsData";
 
 static const char kJSStackContractID[] = "@mozilla.org/js/xpc/ContextStack;1";
 static NS_DEFINE_CID(kParserServiceCID, NS_PARSERSERVICE_CID);
 static NS_DEFINE_CID(kCParserCID, NS_PARSER_CID);
@@ -6035,8 +6038,59 @@ nsContentUtils::LayerManagerForDocument(
 NS_IMPL_ISUPPORTS1(nsIContentUtils, nsIContentUtils)
 
 PRBool
 nsIContentUtils::IsSafeToRunScript()
 {
   return nsContentUtils::IsSafeToRunScript();
 }
 
+already_AddRefed<nsIDocumentLoaderFactory>
+nsIContentUtils::FindInternalContentViewer(const char* aType,
+                                           ContentViewerType* aLoaderType)
+{
+  if (aLoaderType) {
+    *aLoaderType = TYPE_UNSUPPORTED;
+  }
+
+  // one helper factory, please
+  nsCOMPtr<nsICategoryManager> catMan(do_GetService(NS_CATEGORYMANAGER_CONTRACTID));
+  if (!catMan)
+    return NULL;
+
+  FullPagePluginEnabledType pluginEnabled = NOT_ENABLED;
+
+  nsCOMPtr<nsIPluginHost> pluginHost =
+    do_GetService(MOZ_PLUGIN_HOST_CONTRACTID);
+  if (pluginHost) {
+    pluginHost->IsFullPagePluginEnabledForType(aType, &pluginEnabled);
+  }
+
+  nsCOMPtr<nsIDocumentLoaderFactory> docFactory;
+
+  if (OVERRIDE_BUILTIN == pluginEnabled) {
+    docFactory = do_GetService(PLUGIN_DLF_CONTRACTID);
+    if (docFactory && aLoaderType) {
+      *aLoaderType = TYPE_PLUGIN;
+    }
+    return docFactory.forget();
+  }
+
+  nsXPIDLCString contractID;
+  nsresult rv = catMan->GetCategoryEntry("Gecko-Content-Viewers", aType, getter_Copies(contractID));
+  if (NS_SUCCEEDED(rv)) {
+    docFactory = do_GetService(contractID);
+    if (docFactory && aLoaderType) {
+      *aLoaderType = contractID.EqualsLiteral(CONTENT_DLF_CONTRACTID) ? TYPE_CONTENT : TYPE_UNKNOWN;
+    }   
+    return docFactory.forget();
+  }
+
+  if (AVAILABLE == pluginEnabled) {
+    docFactory = do_GetService(PLUGIN_DLF_CONTRACTID);
+    if (docFactory && aLoaderType) {
+      *aLoaderType = TYPE_PLUGIN;
+    }
+    return docFactory.forget();
+  }
+
+  return NULL;
+}

--- a/docshell/base/nsDocShell.cpp
+++ b/docshell/base/nsDocShell.cpp
@@ -44,16 +44,17 @@
 #ifdef MOZ_LOGGING
 // so we can get logging even in release builds (but only for some things)
 #define FORCE_PR_LOG 1
 #endif
 
 #include "nsIBrowserDOMWindow.h"
 #include "nsIComponentManager.h"
 #include "nsIContent.h"
+#include "nsIContentUtils.h"
 #include "mozilla/dom/Element.h"
 #include "nsIDocument.h"
 #include "nsIDOMDocument.h"
 #include "nsIDOM3Document.h"
 #include "nsIDOMNSDocument.h"
 #include "nsIDOMElement.h"
 #include "nsIDOMStorageObsolete.h"
 #include "nsIDOMStorage.h"
@@ -6182,27 +6183,21 @@ nsDocShell::CreateAboutBlankContentViewe
   }
 
   // Now make sure we don't think we're in the middle of firing unload after
   // this point.  This will make us fire unload when the about:blank document
   // unloads... but that's ok, more or less.  Would be nice if it fired load
   // too, of course.
   mFiredUnloadEvent = PR_FALSE;
 
-  // one helper factory, please
-  nsCOMPtr<nsICategoryManager> catMan(do_GetService(NS_CATEGORYMANAGER_CONTRACTID));
-  if (!catMan)
-    return NS_ERROR_FAILURE;
-
-  nsXPIDLCString contractId;
-  rv = catMan->GetCategoryEntry("Gecko-Content-Viewers", "text/html", getter_Copies(contractId));
-  if (NS_FAILED(rv))
-    return rv;
-
-  nsCOMPtr<nsIDocumentLoaderFactory> docFactory(do_GetService(contractId));
+  nsCOMPtr<nsIContentUtils> cutils = do_GetService("@mozilla.org/content/contentutils;1");
+  if (!cutils)
+      return NS_ERROR_FAILURE;
+
+  nsCOMPtr<nsIDocumentLoaderFactory> docFactory = cutils->FindInternalContentViewer("text/html");
   if (docFactory) {
     // generate (about:blank) document to load
     docFactory->CreateBlankDocument(mLoadGroup, aPrincipal,
                                     getter_AddRefs(blankDoc));
     if (blankDoc) {
       // Hack: set the base URI manually, since this document never
       // got Reset() with a channel.
       blankDoc->SetBaseURI(aBaseURI);
@@ -7172,29 +7167,23 @@ nsDocShell::CreateContentViewer(const ch
 nsresult
 nsDocShell::NewContentViewerObj(const char *aContentType,
                                 nsIRequest * request, nsILoadGroup * aLoadGroup,
                                 nsIStreamListener ** aContentHandler,
                                 nsIContentViewer ** aViewer)
 {
     nsCOMPtr<nsIChannel> aOpenedChannel = do_QueryInterface(request);
 
-    nsresult rv;
-    nsCOMPtr<nsICategoryManager> catMan(do_GetService(NS_CATEGORYMANAGER_CONTRACTID, &rv));
-    if (NS_FAILED(rv))
-      return rv;
-    
-    nsXPIDLCString contractId;
-    rv = catMan->GetCategoryEntry("Gecko-Content-Viewers", aContentType, getter_Copies(contractId));
-
-    // Create an instance of the document-loader-factory
-    nsCOMPtr<nsIDocumentLoaderFactory> docLoaderFactory;
-    if (NS_SUCCEEDED(rv))
-        docLoaderFactory = do_GetService(contractId.get());
-
+    nsCOMPtr<nsIContentUtils> cutils = do_GetService("@mozilla.org/content/contentutils;1");
+    if (!cutils) {
+        return NS_ERROR_FAILURE;
+    }
+
+    nsCOMPtr<nsIDocumentLoaderFactory> docLoaderFactory =
+        cutils->FindInternalContentViewer(aContentType);
     if (!docLoaderFactory) {
         return NS_ERROR_FAILURE;
     }
 
     // Now create an instance of the content viewer
     // nsLayoutDLF makes the determination if it should be a "view-source" instead of "view"
     NS_ENSURE_SUCCESS(docLoaderFactory->CreateInstance("view",
                                                        aOpenedChannel,

--- a/docshell/base/nsWebNavigationInfo.cpp
+++ b/docshell/base/nsWebNavigationInfo.cpp
@@ -34,16 +34,17 @@
  * the terms of any one of the MPL, the GPL or the LGPL.
  *
  * ***** END LICENSE BLOCK ***** */
 
 #include "nsWebNavigationInfo.h"
 #include "nsIWebNavigation.h"
 #include "nsString.h"
 #include "nsServiceManagerUtils.h"
+#include "nsIContentUtils.h"
 #include "nsIDocumentLoaderFactory.h"
 #include "nsIPluginHost.h"
 
 NS_IMPL_ISUPPORTS1(nsWebNavigationInfo, nsIWebNavigationInfo)
 
 #define CONTENT_DLF_CONTRACT "@mozilla.org/content/document-loader-factory;1"
 #define PLUGIN_DLF_CONTRACT \
     "@mozilla.org/content/plugin/document-loader-factory;1"
@@ -101,53 +102,47 @@ nsWebNavigationInfo::IsTypeSupported(con
 
   return NS_OK;
 }
 
 nsresult
 nsWebNavigationInfo::IsTypeSupportedInternal(const nsCString& aType,
                                              PRUint32* aIsSupported)
 {
-  NS_PRECONDITION(mCategoryManager, "Must have category manager");
   NS_PRECONDITION(aIsSupported, "Null out param?");
 
-  nsXPIDLCString value;
-  nsresult rv = mCategoryManager->GetCategoryEntry("Gecko-Content-Viewers",
-                                                   aType.get(),
-                                                   getter_Copies(value));
 
-  // If the category manager can't find what we're looking for
-  // it returns NS_ERROR_NOT_AVAILABLE, we don't want to propagate
-  // that to the caller since it's really not a failure
+  nsCOMPtr<nsIContentUtils> cutils = do_GetService("@mozilla.org/content/contentutils;1");
+  if (!cutils)
+      return NS_ERROR_FAILURE;
 
-  if (NS_FAILED(rv) && rv != NS_ERROR_NOT_AVAILABLE)
-    return rv;
+  nsIContentUtils::ContentViewerType vtype = nsIContentUtils::TYPE_UNSUPPORTED;
 
-  // Now try to get an actual document loader factory for this contractid.  If
-  // there is no contractid, don't try and just return false for *aIsSupported.
-  nsCOMPtr<nsIDocumentLoaderFactory> docLoaderFactory;
-  if (!value.IsEmpty()) {
-    docLoaderFactory = do_GetService(value.get());
-  }
+  nsCOMPtr<nsIDocumentLoaderFactory> docLoaderFactory =
+    cutils->FindInternalContentViewer(aType.get(), &vtype);
+  
+  switch (vtype) {
+  case nsIContentUtils::TYPE_UNSUPPORTED:
+    *aIsSupported = nsIWebNavigationInfo::UNSUPPORTED;
+    break;
 
-  // If we got a factory, we should be able to handle this type
-  if (!docLoaderFactory) {
-    *aIsSupported = nsIWebNavigationInfo::UNSUPPORTED;
-  }
-  else if (value.EqualsLiteral(CONTENT_DLF_CONTRACT)) {
+  case nsIContentUtils::TYPE_PLUGIN:
+    *aIsSupported = nsIWebNavigationInfo::PLUGIN;
+    break;
+
+  case nsIContentUtils::TYPE_UNKNOWN:
+    *aIsSupported = nsIWebNavigationInfo::OTHER;
+    break;
+
+  case nsIContentUtils::TYPE_CONTENT:
     PRBool isImage = PR_FALSE;
     mImgLoader->SupportImageWithMimeType(aType.get(), &isImage);
     if (isImage) {
       *aIsSupported = nsIWebNavigationInfo::IMAGE;
     }
     else {
       *aIsSupported = nsIWebNavigationInfo::OTHER;
     }
-  }
-  else if (value.EqualsLiteral(PLUGIN_DLF_CONTRACT)) {
-    *aIsSupported = nsIWebNavigationInfo::PLUGIN;
-  }
-  else {
-    *aIsSupported = nsIWebNavigationInfo::OTHER;
+    break;
   }
   
   return NS_OK;
 }

--- a/layout/build/nsContentDLF.cpp
+++ b/layout/build/nsContentDLF.cpp
@@ -526,17 +526,17 @@ RegisterTypes(nsICategoryManager* aCatMg
     const char* contentType = *aTypes++;
 #ifdef NOISY_REGISTRY
     printf("Register %s => %s\n", contractid, aPath);
 #endif
     // add the MIME types layout can handle to the handlers category.
     // this allows users of layout's viewers (the docshell for example)
     // to query the types of viewers layout can create.
     rv = aCatMgr->AddCategoryEntry("Gecko-Content-Viewers", contentType,
-                                   "@mozilla.org/content/document-loader-factory;1",
+                                   CONTENT_DLF_CONTRACTID,
                                    aPersist, PR_TRUE, nsnull);
     if (NS_FAILED(rv)) break;
   }
   return rv;
 }
 
 static nsresult UnregisterTypes(nsICategoryManager* aCatMgr,
                                 const char* const* aTypes)

--- a/layout/build/nsContentDLF.h
+++ b/layout/build/nsContentDLF.h
@@ -47,16 +47,19 @@ class nsIComponentManager;
 class nsIContentViewer;
 class nsIDocumentViewer;
 class nsIFile;
 class nsIInputStream;
 class nsILoadGroup;
 class nsIStreamListener;
 struct nsModuleComponentInfo;
 
+#define CONTENT_DLF_CONTRACTID "@mozilla.org/content/document-loader-factory;1"
+#define PLUGIN_DLF_CONTRACTID "@mozilla.org/content/plugin/document-loader-factory;1"
+
 class nsContentDLF : public nsIDocumentLoaderFactory
 {
 public:
   nsContentDLF();
   virtual ~nsContentDLF();
 
   NS_DECL_ISUPPORTS
   NS_DECL_NSIDOCUMENTLOADERFACTORY

--- a/layout/build/nsLayoutModule.cpp
+++ b/layout/build/nsLayoutModule.cpp
@@ -1392,17 +1392,17 @@ static const nsModuleComponentInfo gLayo
   { "XML Content Builder",
     NS_XMLCONTENTBUILDER_CID,
     NS_XMLCONTENTBUILDER_CONTRACTID,
     CreateXMLContentBuilder },
 #endif
 
   { "Document Loader Factory",
     NS_CONTENT_DOCUMENT_LOADER_FACTORY_CID,
-    "@mozilla.org/content/document-loader-factory;1",
+    CONTENT_DLF_CONTRACTID,
     CreateContentDLF,
     nsContentDLF::RegisterDocumentFactories,
     nsContentDLF::UnregisterDocumentFactories },
 
   { "Wyciwyg Handler",
     NS_WYCIWYGPROTOCOLHANDLER_CID,
     NS_NETWORK_PROTOCOL_CONTRACTID_PREFIX "wyciwyg",
     nsWyciwygProtocolHandlerConstructor },
@@ -1443,17 +1443,17 @@ static const nsModuleComponentInfo gLayo
   },
 
   // view stuff
   { "View Manager", NS_VIEW_MANAGER_CID, "@mozilla.org/view-manager;1",
     nsViewManagerConstructor },
 
   { "Plugin Document Loader Factory",
     NS_PLUGINDOCLOADERFACTORY_CID,
-    "@mozilla.org/content/plugin/document-loader-factory;1",
+    PLUGIN_DLF_CONTRACTID,
     CreateContentDLF },
 
   { "Plugin Document",
     NS_PLUGINDOCUMENT_CID,
     nsnull,
     CreatePluginDocument },
 
 #ifdef MOZ_MEDIA

--- a/modules/plugin/base/public/nsIPluginHost.idl
+++ b/modules/plugin/base/public/nsIPluginHost.idl
@@ -59,16 +59,33 @@ interface nsIPlugin;
 interface nsIURI;
 interface nsIDOMPlugin;
 interface nsIChannel;
 interface nsIPluginStreamListener;
 
 [ptr] native PRLibraryPtr(PRLibrary);
 [ref] native nsIStreamListenerRef(nsIStreamListener *);
 [ptr] native nsPluginNativeWindowPtr(nsPluginNativeWindow);
+native FullPagePluginEnabledType(FullPagePluginEnabledType);
+
+%{C++
+enum FullPagePluginEnabledType
+{
+    // No plugin was found for this MIME type.
+    NOT_ENABLED,
+
+    // A plugin is available and should take precedence over builtin
+    // content viewers.
+    OVERRIDE_BUILTIN,
+
+    // A plugin is available, but a builtin content viewers should be used if
+    // present.
+    AVAILABLE
+};
+%}    
 
 [scriptable, uuid(D419142E-0571-416B-B797-2A8E6624491D)]
 interface nsIPluginHost : nsISupports
 {
   [noscript] void init();
 
   [noscript] void destroy();
 
@@ -101,16 +118,18 @@ interface nsIPluginHost : nsISupports
 
   [noscript] void setUpPluginInstance(in string aMimeType, in nsIURI aURL, in nsIPluginInstanceOwner aOwner);
 
   // The return code is NS_OK if the plugin is enabled,
   // NS_ERROR_PLUGIN_DISABLED if the plugin is explicitly disabled, and
   // NS_ERROR_FAILURE if there is no plugin for this type.
   [noscript] void isPluginEnabledForType(in string aMimeType);
 
+  [noscript] FullPagePluginEnabledType isFullPagePluginEnabledForType(in string aMimeType);
+
   // The return code is NS_OK if the plugin is enabled and NS_ERROR_FAILURE if
   // the plugin is explicitly disabled or there is no plugin.
   [noscript] void isPluginEnabledForExtension(in string aExtension, in constCharStarRef aMimeType);
 
   [noscript] readonly attribute unsigned long pluginCount;
   
   [noscript] void getPlugins(in unsigned long aPluginCount, out /*array*/ nsIDOMPlugin aPluginArray);
 

--- a/modules/plugin/base/src/nsPluginHost.cpp
+++ b/modules/plugin/base/src/nsPluginHost.cpp
@@ -2605,16 +2605,52 @@ nsPluginHost::IsPluginEnabledForType(con
       return NS_ERROR_PLUGIN_BLOCKLISTED;
     else
       return NS_ERROR_PLUGIN_DISABLED;
   }
 
   return NS_OK;
 }
 
+NS_IMETHODIMP
+nsPluginHost::IsFullPagePluginEnabledForType(const char* aMimeType,
+                                             FullPagePluginEnabledType* aResult)
+{
+  *aResult = NOT_ENABLED;
+
+  nsCOMPtr<nsIPrefBranch> psvc(do_GetService(NS_PREFSERVICE_CONTRACTID));
+  if (!psvc)
+    return NS_OK;
+  
+  // A preference controls whether or not the full page plugin is disabled for
+  // a particular type. The string must be in the form:
+  //   type1,type2,type3,type4
+  // Note: need an actual interface to control this and subsequent disabling 
+  // (and other plugin host settings) so applications can reliably disable 
+  // plugins - without relying on implementation details such as prefs/category
+  // manager entries.
+  nsXPIDLCString overrideTypes;
+  psvc->GetCharPref("plugin.disable_full_page_plugin_for_types", getter_Copies(overrideTypes));
+  overrideTypes.Insert(',', 0);
+  overrideTypes.Append(',');
+  
+  nsCAutoString commaSeparated(',');
+  commaSeparated.Append(aMimeType);
+  commaSeparated.Append(',');
+  if (overrideTypes.Find(commaSeparated) != kNotFound)
+    return NS_OK;
+
+  nsPluginTag* plugin = FindPluginForType(aMimeType, PR_TRUE);
+  if (!plugin || !plugin->IsEnabled())
+    return NS_OK;
+
+  *aResult = mOverrideInternalTypes ? OVERRIDE_BUILTIN : AVAILABLE;
+  return NS_OK;
+}
+
 // check comma delimitered extensions
 static int CompareExtensions(const char *aExtensionList, const char *aExtension)
 {
   if (!aExtensionList || !aExtension)
     return -1;
 
   const char *pExt = aExtensionList;
   const char *pComma = strchr(pExt, ',');
@@ -3349,19 +3385,16 @@ nsresult nsPluginHost::ScanPluginsDirect
       }
     }
 
     // do it if we still want it
     if (bAddIt) {
       pluginTag->SetHost(this);
       pluginTag->mNext = mPlugins;
       mPlugins = pluginTag;
-
-      if (pluginTag->IsEnabled())
-        pluginTag->RegisterWithCategoryManager(mOverrideInternalTypes);
     }
   }
   
   if (warnOutdated)
     mPrefService->SetBoolPref("plugins.update.notifyUser", PR_TRUE);
 
   return NS_OK;
 }

--- a/modules/plugin/base/src/nsPluginTags.cpp
+++ b/modules/plugin/base/src/nsPluginTags.cpp
@@ -407,114 +407,26 @@ nsPluginTag::SetBlocklisted(PRBool aBloc
     Mark(NS_PLUGIN_FLAG_BLOCKLISTED);
   else
     UnMark(NS_PLUGIN_FLAG_BLOCKLISTED);
   
   mPluginHost->UpdatePluginInfo(nsnull);
   return NS_OK;
 }
 
-void
-nsPluginTag::RegisterWithCategoryManager(PRBool aOverrideInternalTypes,
-                                         nsPluginTag::nsRegisterType aType)
-{
-  if (!mMimeTypeArray)
-    return;
-  
-  PLUGIN_LOG(PLUGIN_LOG_NORMAL,
-             ("nsPluginTag::RegisterWithCategoryManager plugin=%s, removing = %s\n",
-              mFileName.get(), aType == ePluginUnregister ? "yes" : "no"));
-  
-  nsCOMPtr<nsICategoryManager> catMan = do_GetService(NS_CATEGORYMANAGER_CONTRACTID);
-  if (!catMan)
-    return;
-  
-  const char *contractId = "@mozilla.org/content/plugin/document-loader-factory;1";
-  
-  nsCOMPtr<nsIPrefBranch> psvc(do_GetService(NS_PREFSERVICE_CONTRACTID));
-  if (!psvc)
-    return; // NS_ERROR_OUT_OF_MEMORY
-  
-  // A preference controls whether or not the full page plugin is disabled for
-  // a particular type. The string must be in the form:
-  //   type1,type2,type3,type4
-  // Note: need an actual interface to control this and subsequent disabling 
-  // (and other plugin host settings) so applications can reliably disable 
-  // plugins - without relying on implementation details such as prefs/category
-  // manager entries.
-  nsXPIDLCString overrideTypes;
-  psvc->GetCharPref("plugin.disable_full_page_plugin_for_types", getter_Copies(overrideTypes));
-  nsCAutoString overrideTypesFormatted;
-  overrideTypesFormatted.Assign(',');
-  overrideTypesFormatted += overrideTypes;
-  overrideTypesFormatted.Append(',');
-  
-  nsACString::const_iterator start, end;
-  for (int i = 0; i < mVariants; i++) {
-    if (aType == ePluginUnregister) {
-      nsXPIDLCString value;
-      if (NS_SUCCEEDED(catMan->GetCategoryEntry("Gecko-Content-Viewers",
-                                                mMimeTypeArray[i],
-                                                getter_Copies(value)))) {
-        // Only delete the entry if a plugin registered for it
-        if (strcmp(value, contractId) == 0) {
-          catMan->DeleteCategoryEntry("Gecko-Content-Viewers",
-                                      mMimeTypeArray[i],
-                                      PR_TRUE);
-        }
-      }
-    } else {
-      overrideTypesFormatted.BeginReading(start);
-      overrideTypesFormatted.EndReading(end);
-      
-      nsDependentCString mimeType(mMimeTypeArray[i]);
-      nsCAutoString commaSeparated; 
-      commaSeparated.Assign(',');
-      commaSeparated += mimeType;
-      commaSeparated.Append(',');
-      if (!FindInReadable(commaSeparated, start, end)) {
-        catMan->AddCategoryEntry("Gecko-Content-Viewers",
-                                 mMimeTypeArray[i],
-                                 contractId,
-                                 PR_FALSE, /* persist: broken by bug 193031 */
-                                 aOverrideInternalTypes, /* replace if we're told to */
-                                 nsnull);
-      }
-    }
-    
-    PLUGIN_LOG(PLUGIN_LOG_NOISY,
-               ("nsPluginTag::RegisterWithCategoryManager mime=%s, plugin=%s\n",
-                mMimeTypeArray[i], mFileName.get()));
-  }
-}
-
 void nsPluginTag::Mark(PRUint32 mask)
 {
   PRBool wasEnabled = IsEnabled();
   mFlags |= mask;
-  // Update entries in the category manager if necessary.
-  if (mPluginHost && wasEnabled != IsEnabled()) {
-    if (wasEnabled)
-      RegisterWithCategoryManager(PR_FALSE, nsPluginTag::ePluginUnregister);
-    else
-      RegisterWithCategoryManager(PR_FALSE, nsPluginTag::ePluginRegister);
-  }
 }
 
 void nsPluginTag::UnMark(PRUint32 mask)
 {
   PRBool wasEnabled = IsEnabled();
   mFlags &= ~mask;
-  // Update entries in the category manager if necessary.
-  if (mPluginHost && wasEnabled != IsEnabled()) {
-    if (wasEnabled)
-      RegisterWithCategoryManager(PR_FALSE, nsPluginTag::ePluginUnregister);
-    else
-      RegisterWithCategoryManager(PR_FALSE, nsPluginTag::ePluginRegister);
-  }
 }
 
 PRBool nsPluginTag::HasFlag(PRUint32 flag)
 {
   return (mFlags & flag) != 0;
 }
 
 PRUint32 nsPluginTag::Flags()
@@ -558,22 +470,16 @@ void nsPluginTag::TryUnloadPlugin()
     nsPluginHost::PostPluginUnloadEvent(mLibrary);
   }
   
   // we should zero it anyway, it is going to be unloaded by
   // CleanUnsedLibraries before we need to call the library
   // again so the calling code should not be fooled and reload
   // the library fresh
   mLibrary = nsnull;
-  
-  // Remove mime types added to the category manager
-  // only if we were made 'active' by setting the host
-  if (mPluginHost) {
-    RegisterWithCategoryManager(PR_FALSE, nsPluginTag::ePluginUnregister);
-  }
 }
 
 /* nsPluginInstanceTag */
 
 nsPluginInstanceTag::nsPluginInstanceTag(nsPluginTag* aPluginTag,
                                          nsIPluginInstance* aInstance,
                                          const char * url)
 {

--- a/modules/plugin/base/src/nsPluginTags.h
+++ b/modules/plugin/base/src/nsPluginTags.h
@@ -61,21 +61,16 @@ struct nsPluginInfo;
 #define NS_PLUGIN_FLAG_UNWANTED     0x0008    // this is an unwanted plugin
 #define NS_PLUGIN_FLAG_BLOCKLISTED  0x0010    // this is a blocklisted plugin
 
 // A linked-list of plugin information that is used for instantiating plugins
 // and reflecting plugin information into JavaScript.
 class nsPluginTag : public nsIPluginTag
 {
 public:
-  enum nsRegisterType {
-    ePluginRegister,
-    ePluginUnregister
-  };
-  
   NS_DECL_ISUPPORTS
   NS_DECL_NSIPLUGINTAG
   
   nsPluginTag(nsPluginTag* aPluginTag);
   nsPluginTag(nsPluginInfo* aPluginInfo);
   nsPluginTag(const char* aName,
               const char* aDescription,
               const char* aFileName,
@@ -93,18 +88,16 @@ public:
   void SetHost(nsPluginHost * aHost);
   void TryUnloadPlugin();
   void Mark(PRUint32 mask);
   void UnMark(PRUint32 mask);
   PRBool HasFlag(PRUint32 flag);
   PRUint32 Flags();
   PRBool Equals(nsPluginTag* aPluginTag);
   PRBool IsEnabled();
-  void RegisterWithCategoryManager(PRBool aOverrideInternalTypes,
-                                   nsRegisterType aType = ePluginRegister);
   
   nsRefPtr<nsPluginTag> mNext;
   nsPluginHost *mPluginHost;
   nsCString     mName; // UTF-8
   nsCString     mDescription; // UTF-8
   PRInt32       mVariants;
   char          **mMimeTypeArray;
   nsTArray<nsCString> mMimeDescriptionArray; // UTF-8