Update sqlite's README.chromium with a note to keep webkit side

third_party/sqlite/README.chromium

 Name: SQLite
 License File: src/LICENSE
 URL: http://sqlite.org/
 
 Instructions for importing a new release of SQLite from sqlite.org.
 
 Note: our current base version is 3.6.18.
 
 First, you need to be on Linux.
 
@@ skipping 24 matching lines @@
 
 # Resolve any conflicts.  Figure out if we've got everything we should
 # have (see below), or if we can omit any changes we no longer need.
 
 # Change to the sqlite directory:
 cd sqlite
 
 # Run the google_generate_preprocessed.sh script:
 ./google_generate_preprocessed.sh
 
+# If there are any updates to os_unix.c, remember to keep
+# WebCore/platform/sql/chromium/SQLiteFileSystemChromiumPosix.cpp in sync.
+# This means preparing a separate patch for WebKit.
+# If you have questions about this part, ask phajdan.jr and dumi.
+
 # Find a sucker.  Send review.
 # TODO(shess) Describe an appropriate comment style.  Seems like it
 # should at least include the SQLite version number.
 
 --------------------------------------------
 
 For reference, all of our local patches are also kept as .patch files in the
 sqlite directory. Here is a list of the patches, in the order they should be
 applied to a vanilla SQLite (of the version we currently have) to get, in
 principle, exactly what is checked in:
@@ skipping 93 matching lines @@
  - fts2_icu.c and fts3_icu.c have a critical bug. U8_NEXT is used over
    a UTF-16 string. It's rep$ by U16_NEXT (jungshik)
  - Added a new function sqlite3Preload we use to prime the database cache. It
    allows much faster performance by reading the file in one contiguous
    operation rather than bringing it in organically, which involves a lot of
    seeking. This change also required sqlite3PcacheGetCachesize to be compiled
    even outside SQLITE_TEST.
  - Added a new function chromium_sqlite3_initialize_win_sqlite3_file()
    at the end of os_win.c. It allows the Windows-specific Chromium VFS
    to reuse most of the win32 SQLite VFS.