[fsp] Add FileStreamReader for the reading operation.

chrome/common/extensions/api/file_system_provider.idl

Index: chrome/common/extensions/api/file_system_provider.idl
diff --git a/chrome/common/extensions/api/file_system_provider.idl b/chrome/common/extensions/api/file_system_provider.idl
index 8b02cffde9de774d48025589c3777a72b81b00f9..bee990382ba3a54a92d124ad80e72337749044fe 100644
--- a/chrome/common/extensions/api/file_system_provider.idl
+++ b/chrome/common/extensions/api/file_system_provider.idl
@@ -85,7 +85,7 @@ namespace fileSystemProvider {
   // data will be returned, then <code>hasNext</code> must be true, and it
   // has to be called again with additional entries. If no more data is
   // available, then <code>hasNext</code> must be set to false.
-  callback FileDataCallback = void(DOMString data, bool hasNext);
+  callback FileDataCallback = void(ArrayBuffer data, bool hasNext);
 
   interface Functions {
     // Mounts a file system with the given <code>displayName</code>.
@@ -145,6 +145,7 @@ namespace fileSystemProvider {
     // exist, then it should be created.
     [maxListeners=1] static void onOpenFileRequested(
         long fileSystemId,
+        long requestId,
         DOMString filePath,
         OpenFileMode mode,
         boolean create,