Support sending a sliced file in chromium....

net/url_request/url_request.h

Index: net/url_request/url_request.h
===================================================================
--- net/url_request/url_request.h	(revision 42417)
+++ net/url_request/url_request.h	(working copy)
@@ -299,12 +299,16 @@
   //
   // When uploading data, bytes_len must be non-zero.
   // When uploading a file range, length must be non-zero. If length
-  // exceeds the end-of-file, the upload is clipped at end-of-file.
+  // exceeds the end-of-file, the upload is clipped at end-of-file. If the
+  // expected modification time is provided (non-zero), it will be used to
+  // check if the underlying file has been changed or not. The granularity of
+  // the time comparison is 1 second since time_t precision is used in WebKit.
   void AppendBytesToUpload(const char* bytes, int bytes_len);
   void AppendFileRangeToUpload(const FilePath& file_path,
-                               uint64 offset, uint64 length);
+                               uint64 offset, uint64 length,
+                               const base::Time& expected_modification_time);
   void AppendFileToUpload(const FilePath& file_path) {
-    AppendFileRangeToUpload(file_path, 0, kuint64max);
+    AppendFileRangeToUpload(file_path, 0, kuint64max, base::Time());
   }
 
   // Set the upload data directly.