diff --git a/mozilla/xpcom/io/nsIFile.idl b/mozilla/xpcom/io/nsIFile.idl
index 616c06a6816..8d428b46238 100644
--- a/mozilla/xpcom/io/nsIFile.idl
+++ b/mozilla/xpcom/io/nsIFile.idl
@@ -229,10 +229,10 @@ interface nsIFile : nsISupports
     boolean equals(in nsIFile inFile);
     
     /**
-     * Will determine the inFile is a descendant
+     * Will determine if the inFile is a descendant
      * If |recur| is true, it will descend subdirectories looking for 
      */
-    boolean isContainedIn(in nsIFile inFile, in boolean recur);
+    boolean contains(in nsIFile inFile, in boolean recur);
 
     /**
      * Parent will be nsnull when this is at the top of the volume.
diff --git a/mozilla/xpcom/io/nsLocalFileMac.cpp b/mozilla/xpcom/io/nsLocalFileMac.cpp
index 2b1093fb12f..eb55956d027 100644
--- a/mozilla/xpcom/io/nsLocalFileMac.cpp
+++ b/mozilla/xpcom/io/nsLocalFileMac.cpp
@@ -1381,7 +1381,7 @@ nsLocalFile::Equals(nsIFile *inFile, PRBool *_retval)
 }
 
 NS_IMETHODIMP
-nsLocalFile::IsContainedIn(nsIFile *inFile, PRBool recur, PRBool *_retval)
+nsLocalFile::Contains(nsIFile *inFile, PRBool recur, PRBool *_retval)
 {
 	*_retval = PR_FALSE;
 	   
diff --git a/mozilla/xpcom/io/nsLocalFileUnix.cpp b/mozilla/xpcom/io/nsLocalFileUnix.cpp
index b91b0ab5e97..33104d94cb2 100644
--- a/mozilla/xpcom/io/nsLocalFileUnix.cpp
+++ b/mozilla/xpcom/io/nsLocalFileUnix.cpp
@@ -986,44 +986,33 @@ nsLocalFile::Equals(nsIFile *inFile, PRBool *_retval)
 }
 
 NS_IMETHODIMP
-nsLocalFile::IsContainedIn(nsIFile *inFile, PRBool recur, PRBool *_retval)
+nsLocalFile::Contains(nsIFile *inFile, PRBool recur, PRBool *_retval)
 {
     NS_ENSURE_ARG(inFile);
     NS_ENSURE_ARG_POINTER(_retval);
-
+   
     nsXPIDLCString inPath;
     nsresult rv;
+    
+    *_retval = PR_FALSE;
 
     if (NS_FAILED(rv = inFile->GetPath(getter_Copies(inPath))))
         return rv;
     
-    ssize_t inLen = strlen(inPath);
+    ssize_t len = strlen(mPath);
 
-    /* remove trailing slashes */
-    while (((const char *)mPath)[inLen - 1] == '/')
-        inLen--;
+    if ( strncmp( mPath, inPath, len) == 0)
+    {
+        // now make sure that the |inFile|'s path has a trailing
+        // separator.
+
+        if (inPath[len] == '/')
+        {
+            *_retval = PR_TRUE;
+        }
 
-    /* 
-     * See if the given path is a prefix of our path, but make sure that
-     * we don't treat /foo as a parent of /foobar/thing.
-     */
-    if (strncmp(inPath, mPath, inLen) || ((const char *)mPath)[inLen] != '/') {
-        *_retval = PR_FALSE;
-        return NS_OK;
-    }
-    if (recur) {
-        /* good enough -- don't need to check for direct parentage */
-        *_retval = PR_TRUE;
-        return NS_OK;
     }
 
-    const char *parentEnd = strrchr(mPath, '/');
-    if (inLen == (parentEnd - (const char *)mPath)) {
-        *_retval = PR_TRUE;
-        return NS_OK;
-    }
-
-    *_retval = PR_FALSE;
     return NS_OK;
 }
 
diff --git a/mozilla/xpcom/io/nsLocalFileWin.cpp b/mozilla/xpcom/io/nsLocalFileWin.cpp
index e52435c43ea..ad39a973636 100644
--- a/mozilla/xpcom/io/nsLocalFileWin.cpp
+++ b/mozilla/xpcom/io/nsLocalFileWin.cpp
@@ -1692,34 +1692,32 @@ nsLocalFile::Equals(nsIFile *inFile, PRBool *_retval)
 }
 
 NS_IMETHODIMP
-nsLocalFile::IsContainedIn(nsIFile *inFile, PRBool recur, PRBool *_retval)
+nsLocalFile::Contains(nsIFile *inFile, PRBool recur, PRBool *_retval)
 {
+    NS_ENSURE_ARG(inFile);
+    NS_ENSURE_ARG_POINTER(_retval);
+   
+    nsXPIDLCString inPath;
+    nsresult rv;
+    
     *_retval = PR_FALSE;
-       
-    char* myFilePath;
-    if ( NS_FAILED(GetTarget(&myFilePath)))
-        GetPath(&myFilePath);
-    
-    PRInt32 myFilePathLen = strlen(myFilePath);
-    
-    char* inFilePath;
-    if ( NS_FAILED(inFile->GetTarget(&inFilePath)))
-        inFile->GetPath(&inFilePath);
 
-    if ( strncmp( myFilePath, inFilePath, myFilePathLen) == 0)
+    if (NS_FAILED(rv = inFile->GetPath(getter_Copies(inPath))))
+        return rv;
+    
+    size_t len = strlen(mPath);   
+ 
+    if ( strncmp( mPath, inPath, len) == 0)
     {
         // now make sure that the |inFile|'s path has a trailing
         // separator.
 
-        if (inFilePath[myFilePathLen] == '\\')
+        if (inPath[len] == '\\')
         {
             *_retval = PR_TRUE;
         }
 
     }
-        
-    nsAllocator::Free(inFilePath);
-    nsAllocator::Free(myFilePath);
 
     return NS_OK;
 }