--- a/chrome/nsChromeRegistry.cpp
+++ b/chrome/nsChromeRegistry.cpp
@@ -288,26 +288,16 @@ nsChromeRegistry::ConvertChromeURL(nsIUR
 
   nsIURI* baseURI = GetBaseURIFromPackage(package, provider, path);
 
   uint32_t flags;
   rv = GetFlagsFromPackage(package, &flags);
   if (NS_FAILED(rv))
     return rv;
 
-  if (flags & PLATFORM_PACKAGE) {
-#if defined(XP_WIN)
-    path.Insert("win/", 0);
-#elif defined(XP_MACOSX)
-    path.Insert("mac/", 0);
-#else
-    path.Insert("unix/", 0);
-#endif
-  }
-
   if (!baseURI) {
     LogMessage("No chrome package registered for chrome://%s/%s/%s",
                package.get(), provider.get(), path.get());
     return NS_ERROR_FILE_NOT_FOUND;
   }
 
   return NS_NewURI(aResult, path, nullptr, baseURI);
 }

--- a/chrome/nsChromeRegistry.h
+++ b/chrome/nsChromeRegistry.h
@@ -135,20 +135,16 @@ public:
                              char *const * argv, int flags) = 0;
   virtual void ManifestOverride(ManifestProcessingContext& cx, int lineno,
                                 char *const * argv, int flags) = 0;
   virtual void ManifestResource(ManifestProcessingContext& cx, int lineno,
                                 char *const * argv, int flags) = 0;
 
   // Available flags
   enum {
-    // This is a "platform" package (e.g. chrome://global-platform/).
-    // Appends one of win/ unix/ mac/ to the base URI.
-    PLATFORM_PACKAGE = 1 << 0,
-
     // This package should use the new XPCNativeWrappers to separate
     // content from chrome. This flag is currently unused (because we call
     // into xpconnect at registration time).
     XPCNATIVEWRAPPERS = 1 << 1,
 
     // Content script may access files in this package
     CONTENT_ACCESSIBLE = 1 << 2,
 

--- a/xpcom/components/ManifestParser.cpp
+++ b/xpcom/components/ManifestParser.cpp
@@ -51,17 +51,17 @@ struct ManifestDirective
 
   // Some directives should only be delivered for APP or EXTENSION locations.
   bool componentonly;
 
   bool ischrome;
 
   bool allowbootstrap;
 
-  // The platform/contentaccessible flags only apply to content directives.
+  // The contentaccessible flags only apply to content directives.
   bool contentflags;
 
   // Function to handle this directive. This isn't a union because C++ still
   // hasn't learned how to initialize unions in a sane way.
   void (nsComponentManagerImpl::*mgrfunc)(
     nsComponentManagerImpl::ManifestProcessingContext& aCx,
     int aLineNo, char* const* aArgv);
   void (nsChromeRegistry::*regfunc)(
@@ -444,17 +444,16 @@ void
 ParseManifest(NSLocationType aType, FileLocation& aFile, char* aBuf,
               bool aChromeOnly, bool aXPTOnly)
 {
   nsComponentManagerImpl::ManifestProcessingContext mgrcx(aType, aFile,
                                                           aChromeOnly);
   nsChromeRegistry::ManifestProcessingContext chromecx(aType, aFile);
   nsresult rv;
 
-  NS_NAMED_LITERAL_STRING(kPlatform, "platform");
   NS_NAMED_LITERAL_STRING(kContentAccessible, "contentaccessible");
   NS_NAMED_LITERAL_STRING(kRemoteEnabled, "remoteenabled");
   NS_NAMED_LITERAL_STRING(kRemoteRequired, "remoterequired");
   NS_NAMED_LITERAL_STRING(kApplication, "application");
   NS_NAMED_LITERAL_STRING(kAppVersion, "appversion");
   NS_NAMED_LITERAL_STRING(kGeckoVersion, "platformversion");
   NS_NAMED_LITERAL_STRING(kOs, "os");
   NS_NAMED_LITERAL_STRING(kOsVersion, "osversion");
@@ -680,21 +679,16 @@ ParseManifest(NSLocationType aType, File
       if (CheckFlag(kTablet, wtoken, tablet)) {
         stTablet = (tablet == isTablet) ? eOK : eBad;
         continue;
       }
 #endif
 
       if (directive->contentflags) {
         bool flag;
-        if (CheckFlag(kPlatform, wtoken, flag)) {
-          if (flag)
-            flags |= nsChromeRegistry::PLATFORM_PACKAGE;
-          continue;
-        }
         if (CheckFlag(kContentAccessible, wtoken, flag)) {
           if (flag)
             flags |= nsChromeRegistry::CONTENT_ACCESSIBLE;
           continue;
         }
         if (CheckFlag(kRemoteEnabled, wtoken, flag)) {
           if (flag)
             flags |= nsChromeRegistry::REMOTE_ALLOWED;