[websql] Guard against vfs method deprecation.

third_party/WebKit/Source/modules/webdatabase/sqlite/SQLiteFileSystemWin.cpp

 /*
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 140 matching lines @@
 }
 
 int chromiumCurrentTime(sqlite3_vfs *vfs, double *prNow)
 {
     sqlite3_vfs* wrappedVfs = static_cast<sqlite3_vfs*>(vfs->pAppData);
     return wrappedVfs->xCurrentTime(wrappedVfs, prNow);
 }
 
 int chromiumGetLastError(sqlite3_vfs *vfs, int e, char* s)
 {
-    sqlite3_vfs* wrappedVfs = static_cast<sqlite3_vfs*>(vfs->pAppData);
-    return wrappedVfs->xGetLastError(wrappedVfs, e, s);
+    return SQLITE_ERROR;

[michaeln, 2016/01/26 21:59:34]

What's going on with this function? Can you update the comment about it too.

[Scott Hess - ex-Googler, 2016/01/26 23:44:24]

OK.

SQLite introduced this at one point and then never used it, so it seemed safer
to fail safe rather than depend on the underlying VFS implementation.  The
current os_unix.c implementation returns 0 (SQLITE_OK) and says it is never
called (and it was removed entirely at the same time as unixGetCurrentTime).

Hmm.  Your question caused me to look over at the os_win.c implementation.  It
basically returns FormatMessage() results, though it's still never called.  The
docs there do indicate that returning 0 with an empty buffer is an appropriate
implementation.  So going with that.

[The online docs list xGetLastError with no description at all :-).]

 }
 
 } // namespace
 
 void SQLiteFileSystem::registerSQLiteVFS()
 {
     sqlite3_vfs* wrappedVfs = sqlite3_vfs_find("win32");
+
+    // These are implemented by delegating to |wrappedVfs|.
+    // TODO(shess): Implement local versions.
+    ASSERT(wrappedVfs->xRandomness);
+    ASSERT(wrappedVfs->xSleep);
+    ASSERT(wrappedVfs->xCurrentTime);
+
     static sqlite3_vfs chromium_vfs = {
         1,
         wrappedVfs->szOsFile,
         wrappedVfs->mxPathname,
         0,
         "chromium_vfs",
         wrappedVfs,
         chromiumOpen,
         chromiumDelete,
         chromiumAccess,
         chromiumFullPathname,
         chromiumDlOpen,
         chromiumDlError,
         chromiumDlSym,
         chromiumDlClose,
         chromiumRandomness,
         chromiumSleep,
         chromiumCurrentTime,
         chromiumGetLastError
     };
     sqlite3_vfs_register(&chromium_vfs, 0);
 }
 
 } // namespace blink