diff --git a/mozilla/xpcom/build/nsXPComInit.cpp b/mozilla/xpcom/build/nsXPComInit.cpp
index 86690df7b98..5062a535578 100644
--- a/mozilla/xpcom/build/nsXPComInit.cpp
+++ b/mozilla/xpcom/build/nsXPComInit.cpp
@@ -104,6 +104,7 @@
 
 #include "nsStringStream.h"
 extern NS_METHOD nsStringInputStreamConstructor(nsISupports *, REFNSIID, void **);
+NS_DECL_CLASSINFO(nsStringInputStream)
 
 #include "nsFastLoadService.h"
 
@@ -387,7 +388,8 @@ static const nsModuleComponentInfo components[] = {
     COMPONENT(PROCESS, nsProcessConstructor),
     COMPONENT(ENVIRONMENT, nsEnvironment::Create),
 
-    COMPONENT(STRINGINPUTSTREAM, nsStringInputStreamConstructor),
+    COMPONENT_CI_FLAGS(STRINGINPUTSTREAM, nsStringInputStreamConstructor,
+                       nsStringInputStream, nsIClassInfo::THREADSAFE),
     COMPONENT(MULTIPLEXINPUTSTREAM, nsMultiplexInputStreamConstructor),
 
 #ifndef MOZ_NO_FAST_LOAD
diff --git a/mozilla/xpcom/io/nsIStringStream.idl b/mozilla/xpcom/io/nsIStringStream.idl
index 4f482e71690..c2354bf9603 100644
--- a/mozilla/xpcom/io/nsIStringStream.idl
+++ b/mozilla/xpcom/io/nsIStringStream.idl
@@ -93,22 +93,3 @@ interface nsIStringInputStream : nsIInputStream
      */
     [noscript] void shareData(in string data, in long dataLen);
 };
-
-/**
- * This interface provides a convenient attribute for setting and getting the
- * stream's data.
- */
-[scriptable, uuid(0e36fe9e-ecbe-4088-b616-45672d1c3e94)]
-interface nsIStringInputStream2 : nsIStringInputStream
-{
-    /**
-     * Set or get this stream's data.  The data may contain null characters.
-     *
-     * NOTE: JS callers should understand that assigning a JS string to this
-     * attribute results in the high-byte of each character being discarded.
-     * Likewise, assigning this attribute into a JS string results in the
-     * high-byte of each character in the resulting JS string being set to
-     * zero.
-     */
-    attribute ACString data;
-};
diff --git a/mozilla/xpcom/io/nsStringStream.cpp b/mozilla/xpcom/io/nsStringStream.cpp
index 8df32f751d4..8c1413f8607 100644
--- a/mozilla/xpcom/io/nsStringStream.cpp
+++ b/mozilla/xpcom/io/nsStringStream.cpp
@@ -54,27 +54,29 @@
 
 #include "nsStringStream.h"
 #include "nsStreamUtils.h"
-
+#include "nsReadableUtils.h"
+#include "nsISeekableStream.h"
+#include "nsISupportsPrimitives.h"
+#include "nsInt64.h"
+#include "nsCRT.h"
 #include "prerror.h"
 #include "plstr.h"
-#include "nsReadableUtils.h"
-#include "nsCRT.h"
-#include "nsISeekableStream.h"
-#include "nsInt64.h"
 
 //-----------------------------------------------------------------------------
 // nsIStringInputStream implementation
 //-----------------------------------------------------------------------------
 
-class nsStringInputStream : public nsIStringInputStream2
+class nsStringInputStream : public nsIStringInputStream
                           , public nsISeekableStream
+                          , public nsISupportsCString
 {
 public:
     NS_DECL_ISUPPORTS
     NS_DECL_NSIINPUTSTREAM
     NS_DECL_NSISTRINGINPUTSTREAM
-    NS_DECL_NSISTRINGINPUTSTREAM2
     NS_DECL_NSISEEKABLESTREAM
+    NS_DECL_NSISUPPORTSPRIMITIVE
+    NS_DECL_NSISUPPORTSCSTRING
 
     nsStringInputStream()
         : mData(nsnull)
@@ -113,20 +115,38 @@ private:
 
 // This class needs to support threadsafe refcounting since people often
 // allocate a string stream, and then read it from a background thread.
-NS_IMPL_THREADSAFE_ISUPPORTS4(nsStringInputStream,
-                              nsIStringInputStream,
-                              nsIStringInputStream2,
-                              nsIInputStream,
-                              nsISeekableStream)
+NS_IMPL_THREADSAFE_ADDREF(nsStringInputStream)
+NS_IMPL_THREADSAFE_RELEASE(nsStringInputStream)
+
+NS_IMPL_QUERY_INTERFACE4_CI(nsStringInputStream,
+                            nsIStringInputStream,
+                            nsIInputStream,
+                            nsISupportsCString,
+                            nsISeekableStream)
+NS_IMPL_CI_INTERFACE_GETTER4(nsStringInputStream,
+                             nsIStringInputStream,
+                             nsIInputStream,
+                             nsISupportsCString,
+                             nsISeekableStream)
 
 /////////
-// nsIStringInputStream2 implementation
+// nsISupportsCString implementation
 /////////
 
+NS_IMETHODIMP
+nsStringInputStream::GetType(PRUint16 *type)
+{
+    *type = TYPE_CSTRING;
+    return NS_OK;
+}
+
 NS_IMETHODIMP
 nsStringInputStream::GetData(nsACString &data)
 {
-    NS_ENSURE_TRUE(mData, NS_ERROR_NOT_INITIALIZED);
+    // The stream doesn't have any data when it is closed.  We could fake it
+    // and return an empty string here, but it seems better to keep this return
+    // value consistent with the behavior of the other 'getter' methods.
+    NS_ENSURE_TRUE(mData, NS_BASE_STREAM_CLOSED);
 
     data.Assign(mData, mLength);
     return NS_OK;
@@ -140,6 +160,13 @@ nsStringInputStream::SetData(const nsACString &data)
     return SetData(iter.get(), iter.size_forward());
 }
 
+NS_IMETHODIMP
+nsStringInputStream::ToString(char **result)
+{
+    // NOTE: This method may result in data loss, so we do not implement it.
+    return NS_ERROR_NOT_IMPLEMENTED;
+}
+
 /////////
 // nsIStringInputStream implementation
 /////////