[tracing] Add sqlite memory statistics to tracing.

sql/connection.h

Index: sql/connection.h
diff --git a/sql/connection.h b/sql/connection.h
index 19592d9f0e44ed68764b9d25a88d9a65424ba9b7..a79fe56bedc923dc5758bb9e49eb27a9e70263e0 100644
--- a/sql/connection.h
+++ b/sql/connection.h
@@ -18,6 +18,7 @@
 #include "base/memory/scoped_ptr.h"
 #include "base/threading/thread_restrictions.h"
 #include "base/time/time.h"
+#include "base/trace_event/memory_dump_provider.h"
 #include "sql/sql_export.h"
 
 struct sqlite3;
@@ -102,7 +103,7 @@ class SQL_EXPORT TimeSource {
   DISALLOW_COPY_AND_ASSIGN(TimeSource);
 };
 
-class SQL_EXPORT Connection {
+class SQL_EXPORT Connection : public base::trace_event::MemoryDumpProvider {
  private:

[Primiano Tucci (use gerrit), 2015/09/30 10:26:56]

Just to have a rough idea, how many connections can we have open?
Is it a few, dozens or hundreds?

[ssid, 2015/10/02 17:06:10]

It is usually less than 2 dozens.

   class StatementRef;  // Forward declaration, see real one below.
 
@@ -110,7 +111,7 @@ class SQL_EXPORT Connection {
   // The database is opened by calling Open[InMemory](). Any uncommitted
   // transactions will be rolled back when this object is deleted.
   Connection();
-  ~Connection();
+  ~Connection() override;
 
   // Pre-init configuration ----------------------------------------------------
 
@@ -461,6 +462,11 @@ class SQL_EXPORT Connection {
   // tests.
   static bool ShouldIgnoreSqliteError(int error);
 
+  // base::trace_event::MemoryDumpProvider implementation.
+  bool OnMemoryDump(
+      const base::trace_event::MemoryDumpArgs& args,
+      base::trace_event::ProcessMemoryDump* process_memory_dump) override;
+
  private:
   // For recovery module.
   friend class Recovery;