diff --git a/mozilla/xpcom/io/nsILocalFileWin.idl b/mozilla/xpcom/io/nsILocalFileWin.idl
index 36d7e036aa7..b51ac82ce0e 100644
--- a/mozilla/xpcom/io/nsILocalFileWin.idl
+++ b/mozilla/xpcom/io/nsILocalFileWin.idl
@@ -39,7 +39,7 @@
 
 #include "nsILocalFile.idl"
 
-[scriptable, uuid(dc42f467-4094-437d-9e3e-8912a072aede)]
+[scriptable, uuid(def38371-73b0-4dfd-85cd-0a7c91afbec6)]
 interface nsILocalFileWin : nsILocalFile
 {
    /**
@@ -52,5 +52,17 @@ interface nsILocalFileWin : nsILocalFile
     *
     */
     AString getVersionInfoField(in string aField);
+
+    /**
+     * The canonical path of the file, which avoids short/long
+     * pathname inconsistencies. The nsILocalFile persistent
+     * descriptor is not guaranteed to be canonicalized (it may
+     * persist either the long or the short path name). The format of
+     * the canonical path will vary with the underlying file system:
+     * it will typically be the short pathname on filesystems that
+     * support both short and long path forms.
+     */
+    readonly attribute AString canonicalPath;
+    [noscript] readonly attribute ACString nativeCanonicalPath;
 };
 
diff --git a/mozilla/xpcom/io/nsLocalFile.h b/mozilla/xpcom/io/nsLocalFile.h
index 58c85f82bb4..09e63643985 100644
--- a/mozilla/xpcom/io/nsLocalFile.h
+++ b/mozilla/xpcom/io/nsLocalFile.h
@@ -47,6 +47,8 @@
 #ifndef _NS_LOCAL_FILE_H_
 #define _NS_LOCAL_FILE_H_
 
+#include "nscore.h"
+
 #define NS_LOCAL_FILE_CID {0x2e23e220, 0x60be, 0x11d3, {0x8c, 0x4a, 0x00, 0x00, 0x64, 0x65, 0x73, 0x74}}
 
 #define NS_DECL_NSLOCALFILE_UNICODE_METHODS                                                      \
diff --git a/mozilla/xpcom/io/nsLocalFileWin.cpp b/mozilla/xpcom/io/nsLocalFileWin.cpp
index 65e3794b4a8..a51062c86c0 100644
--- a/mozilla/xpcom/io/nsLocalFileWin.cpp
+++ b/mozilla/xpcom/io/nsLocalFileWin.cpp
@@ -52,6 +52,7 @@
 #include "prtypes.h"
 #include "prio.h"
 #include "prprf.h"
+#include "nsHashKeys.h"
 
 #include "nsXPIDLString.h"
 #include "nsReadableUtils.h"
@@ -452,7 +453,6 @@ NS_IMPL_ISUPPORTS2(nsDirEnumerator, nsISimpleEnumerator, nsIDirectoryEnumerator)
 nsLocalFile::nsLocalFile()
   : mDirty(PR_TRUE)
   , mFollowSymlinks(PR_FALSE)
-  , mHashCode(0)
 {
 }
 
@@ -495,7 +495,6 @@ nsLocalFile::nsLocalFile(const nsLocalFile& other)
   : mDirty(PR_TRUE)
   , mFollowSymlinks(other.mFollowSymlinks)
   , mWorkingPath(other.mWorkingPath)
-  , mHashCode(0)
 {
 }
 
@@ -2160,26 +2159,20 @@ nsLocalFile::Equals(nsIFile *inFile, PRBool *_retval)
     NS_ENSURE_ARG(inFile);
     NS_ENSURE_ARG(_retval);
 
+    EnsureShortPath();
+
+    nsCOMPtr<nsILocalFileWin> lf(do_QueryInterface(inFile));
+    if (!lf) {
+        *_retval = PR_FALSE;
+        return NS_OK;
+    }
+
     nsCAutoString inFilePath;
-    inFile->GetNativePath(inFilePath);
+    lf->GetNativeCanonicalPath(inFilePath);
 
-    // Normalize both paths to the short form, failing back to a string
-    // comparison of the long form.
+    *_retval = _mbsicmp((unsigned char*) mShortWorkingPath.get(),
+                        (unsigned char*) inFilePath.get()) == 0;
 
-    char thisshort[MAX_PATH];
-    char thatshort[MAX_PATH];
-
-    DWORD thisr = GetShortPathName(mWorkingPath.get(), thisshort, sizeof(thisshort));
-    DWORD thatr = GetShortPathName(inFilePath.get(), thatshort, sizeof(thatshort));
-
-    if (thisr && thatr && thisr < sizeof(thisshort) && thatr < sizeof(thatshort)) {
-        *_retval = (_mbsicmp((unsigned char*) thisshort,
-                             (unsigned char*) thatshort) == 0);
-    }
-    else {
-        *_retval = (_mbsicmp((unsigned char*) inFilePath.get(),
-                             (unsigned char*) mWorkingPath.get()) == 0);
-    }
     return NS_OK;
 }
 
@@ -2544,23 +2537,45 @@ nsLocalFile::Equals(nsIHashable* aOther, PRBool *aResult)
     return Equals(otherfile, aResult);
 }
 
+void
+nsLocalFile::EnsureShortPath()
+{
+    if (!mShortWorkingPath.IsEmpty())
+        return;
+
+    char thisshort[MAX_PATH];
+    DWORD thisr = GetShortPathName(mWorkingPath.get(),
+                                   thisshort, sizeof(thisshort));
+    if (thisr < sizeof(thisshort))
+        mShortWorkingPath.Assign(thisshort);
+    else
+        mShortWorkingPath.Assign(mWorkingPath);
+}
+
+NS_IMETHODIMP
+nsLocalFile::GetNativeCanonicalPath(nsACString &aResult)
+{
+    EnsureShortPath();
+    aResult.Assign(mShortWorkingPath);
+    return NS_OK;
+}
+
+NS_IMETHODIMP
+nsLocalFile::GetCanonicalPath(nsAString &aResult)
+{
+    EnsureShortPath();
+    NS_CopyNativeToUnicode(mShortWorkingPath, aResult);
+    return NS_OK;
+}
+
 NS_IMETHODIMP
 nsLocalFile::GetHashCode(PRUint32 *aResult)
 {
-    if (!mHashCode) {
-        // In order for short and long path names to hash to the same value we
-        // always hash on the short pathname.
+    // In order for short and long path names to hash to the same value we
+    // always hash on the short pathname.
+    EnsureShortPath();
 
-        char thisshort[MAX_PATH];
-        DWORD thisr = GetShortPathName(mWorkingPath.get(),
-                                       thisshort, sizeof(thisshort));
-        if (thisr < sizeof(thisshort))
-            mHashCode = nsCRT::HashCode(thisshort);
-        else
-            mHashCode = nsCRT::HashCode(mWorkingPath.get());
-    }
-
-    *aResult = mHashCode;
+    *aResult = HashString(mShortWorkingPath);
     return NS_OK;
 }
 
diff --git a/mozilla/xpcom/io/nsLocalFileWin.h b/mozilla/xpcom/io/nsLocalFileWin.h
index 44bed6105e1..f51d411f262 100644
--- a/mozilla/xpcom/io/nsLocalFileWin.h
+++ b/mozilla/xpcom/io/nsLocalFileWin.h
@@ -1,4 +1,4 @@
-/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
 /* ***** BEGIN LICENSE BLOCK *****
  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
  *
@@ -104,13 +104,18 @@ private:
     // this will be the resolved path of shortcuts, it will *NEVER* be returned to the user
     nsCString mResolvedPath;
     
-    PRFileInfo64 mFileInfo64;
-    PRUint32 mHashCode;
+    // this string, if not empty, is the *short* pathname that represents
+    // mWorkingPath
+    nsCString mShortWorkingPath;
 
-    void MakeDirty() { mDirty = PR_TRUE; mHashCode = 0; }
+    PRFileInfo64 mFileInfo64;
+
+    void MakeDirty() { mDirty = PR_TRUE; mShortWorkingPath.Truncate(); }
 
     nsresult ResolveAndStat();
     nsresult ResolveShortcut();
+
+    void EnsureShortPath();
     
     nsresult CopyMove(nsIFile *newParentDir, const nsACString &newName, PRBool followSymlinks, PRBool move);
     nsresult CopySingleFile(nsIFile *source, nsIFile* dest, const nsACString &newName, PRBool followSymlinks, PRBool move);