Add flag to disable mmap in all sql connection

sql/connection.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "sql/connection.h"
 
 #include <limits.h>
 #include <stddef.h>
 #include <stdint.h>
 #include <string.h>
@@ skipping 25 matching lines @@
 #include "third_party/sqlite/src/ext/icu/sqliteicu.h"
 #endif
 
 namespace {
 
 // Spin for up to a second waiting for the lock to clear when setting
 // up the database.
 // TODO(shess): Better story on this.  http://crbug.com/56559
 const int kBusyTimeoutSeconds = 1;
 
+bool g_mmap_disabled_default = false;
+
 class ScopedBusyTimeout {
  public:
   explicit ScopedBusyTimeout(sqlite3* db)
       : db_(db) {
   }
   ~ScopedBusyTimeout() {
     sqlite3_busy_timeout(db_, 0);
   }
 
   int SetTimeout(base::TimeDelta timeout) {
@@ skipping 191 matching lines @@
   int basic_error = error & 0xff;
 
   // These errors relate more to the runtime context of the system than to
   // errors with a SQL statement or with the schema, so they aren't generally
   // interesting to flag.  This list is not comprehensive.
   return basic_error == SQLITE_BUSY ||
       basic_error == SQLITE_NOTADB ||
       basic_error == SQLITE_CORRUPT;
 }
 
+// static
+void Connection::set_mmap_disabled_by_default() {
+    g_mmap_disabled_default = true;
+}
+
+
 void Connection::ReportDiagnosticInfo(int extended_error, Statement* stmt) {
   AssertIOAllowed();
 
   std::string debug_info;
   const int error = (extended_error & 0xFF);
   if (error == SQLITE_CORRUPT) {
     debug_info = CollectCorruptionInfo();
   } else {
     debug_info = CollectErrorInfo(extended_error, stmt);
   }
@@ skipping 65 matching lines @@
 Connection::Connection()
     : db_(NULL),
       page_size_(0),
       cache_size_(0),
       exclusive_locking_(false),
       restrict_to_user_(false),
       transaction_nesting_(0),
       needs_rollback_(false),
       in_memory_(false),
       poisoned_(false),
-      mmap_disabled_(false),
+      mmap_disabled_(g_mmap_disabled_default),
       mmap_enabled_(false),
       total_changes_at_last_release_(0),
       stats_histogram_(NULL),
       commit_time_histogram_(NULL),
       autocommit_time_histogram_(NULL),
       update_time_histogram_(NULL),
       query_time_histogram_(NULL),
       clock_(new TimeSource()) {
 }
 
@@ skipping 1606 matching lines @@
   ignore_result(Execute(kNoWritableSchema));
 
   return ret;
 }
 
 base::TimeTicks TimeSource::Now() {
   return base::TimeTicks::Now();
 }
 
 }  // namespace sql