FileAPI: Compare expected modification time with delta on file read

storage/browser/fileapi/file_stream_reader.cc

Index: storage/browser/fileapi/file_stream_reader.cc
diff --git a/storage/browser/fileapi/file_stream_reader.cc b/storage/browser/fileapi/file_stream_reader.cc
index cb87ecb939ba4b96a5d6f56a565626b8ece0c47e..00d3e22bd00cf1b532887ed3ddfcc1de083703fa 100644
--- a/storage/browser/fileapi/file_stream_reader.cc
+++ b/storage/browser/fileapi/file_stream_reader.cc
@@ -8,13 +8,18 @@
 
 namespace storage {
 
+// Int64->double->int64 conversions (e.g. through Blink) may lose some
+// precision in the microsecond range. Allow 10us delta.
+const int kModificationTimeAllowedDeltaMicroseconds = 10;
+
 // Verify if the underlying file has not been modified.
 bool FileStreamReader::VerifySnapshotTime(
     const base::Time& expected_modification_time,
     const base::File::Info& file_info) {
   return expected_modification_time.is_null() ||
-         expected_modification_time.ToTimeT() ==
-             file_info.last_modified.ToTimeT();
+         (expected_modification_time - file_info.last_modified)
+                 .magnitude()
+                 .InMicroseconds() < kModificationTimeAllowedDeltaMicroseconds;
 }
 
 }  // namespace storage