Add flag to disable mmap in all sql connection

sql/connection.cc

Index: sql/connection.cc
diff --git a/sql/connection.cc b/sql/connection.cc
index 003005a8e6294247df3d5bbea887a54ccd365cd7..20dfb323ee2d4100f2ab80b23ff8a00256634843 100644
--- a/sql/connection.cc
+++ b/sql/connection.cc
@@ -43,6 +43,8 @@ namespace {
 // TODO(shess): Better story on this.  http://crbug.com/56559
 const int kBusyTimeoutSeconds = 1;
 
+bool mmap_disabled_default = false;

[Scott Hess - ex-Googler, 2016/01/26 21:51:08]

Probably needs to be g_mmap_disabled_default, I think.

[vichang1, 2016/01/27 15:19:16]

done.

+
 class ScopedBusyTimeout {
  public:
   explicit ScopedBusyTimeout(sqlite3* db)
@@ -254,6 +256,12 @@ bool Connection::ShouldIgnoreSqliteCompileError(int error) {
       basic_error == SQLITE_CORRUPT;
 }
 
+// static
+void Connection::set_mmap_disabled_by_default() {
+    mmap_disabled_default = true;
+}
+
+
 void Connection::ReportDiagnosticInfo(int extended_error, Statement* stmt) {
   AssertIOAllowed();
 
@@ -339,7 +347,7 @@ Connection::Connection()
       needs_rollback_(false),
       in_memory_(false),
       poisoned_(false),
-      mmap_disabled_(false),
+      mmap_disabled_(mmap_disabled_default),
       mmap_enabled_(false),
       total_changes_at_last_release_(0),
       stats_histogram_(NULL),