[sql] Fix error in Preload size.

Was using file size rather than limiting to file size.

BUG=none

Review URL: https://codereview.chromium.org/1096113002

Cr-Commit-Position: refs/heads/master@{#326064}
diff --git a/sql/connection.cc b/sql/connection.cc
index d94b4d8..ba799a90 100644
--- a/sql/connection.cc
+++ b/sql/connection.cc
@@ -340,7 +340,7 @@
     preload_size = file_size;
 
   scoped_ptr<char[]> buf(new char[page_size]);
-  for (sqlite3_int64 pos = 0; pos < file_size; pos += page_size) {
+  for (sqlite3_int64 pos = 0; pos < preload_size; pos += page_size) {
     rc = file->pMethods->xRead(file, buf.get(), page_size, pos);
     if (rc != SQLITE_OK)
       return;