[IndexedDB] Added IndexedDBCursor lifetime tracing

content/browser/indexed_db/indexed_db_cursor.cc

 // Copyright (c) 2013 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 "content/browser/indexed_db/indexed_db_cursor.h"
 
 #include <stddef.h>
 #include <utility>
 #include <vector>
 
@@ skipping 47 matching lines @@
 IndexedDBCursor::IndexedDBCursor(
     std::unique_ptr<IndexedDBBackingStore::Cursor> cursor,
     indexed_db::CursorType cursor_type,
     blink::WebIDBTaskType task_type,
     IndexedDBTransaction* transaction)
     : task_type_(task_type),
       cursor_type_(cursor_type),
       transaction_(transaction),
       cursor_(std::move(cursor)),
       closed_(false),
-      ptr_factory_(this) {}
+      ptr_factory_(this) {
+  IDB_ASYNC_TRACE_BEGIN("IndexedDBCursor::lifetime", this);
+}
 
-IndexedDBCursor::~IndexedDBCursor() {}
+IndexedDBCursor::~IndexedDBCursor() {
+  if (!closed_) {

[cmumford, 2017/03/14 16:30:56]

Nit: How about Having ::Close() to a:

  if (closed_)
    return;

and then remove the check from the destructor. C++ call tail optimization should
make it equally efficient.

[dmurph, 2017/03/29 23:02:19]

Done.

+    // Call to make sure we complete our lifetime trace.
+    Close();
+  }
+}
 
 void IndexedDBCursor::Continue(std::unique_ptr<IndexedDBKey> key,
                                std::unique_ptr<IndexedDBKey> primary_key,
                                scoped_refptr<IndexedDBCallbacks> callbacks) {
   IDB_TRACE("IndexedDBCursor::Continue");
 
   if (closed_) {
     callbacks->OnError(CreateCursorClosedError());
     return;
   }
@@ skipping 180 matching lines @@
     for (int i = 0; i < used_prefetches - 1; ++i) {
       bool ok = cursor_->Continue(&s);
       DCHECK(ok);
     }
   }
 
   return s;
 }
 
 void IndexedDBCursor::Close() {
+  IDB_ASYNC_TRACE_END("IndexedDBCursor::lifetime", this);

[cmumford, 2017/03/14 16:30:56]

::lifetime is better called from the destructor since there's no guarantee how
long the owner may hold on to a cursor after it is closed. I realize that it's
the end of it's "effective" lifetime, but since the object still "lives" on, the
name or call site seem out of place.

[dmurph, 2017/03/29 23:02:19]

Changed to ::open

   IDB_TRACE("IndexedDBCursor::Close");
   closed_ = true;
   cursor_.reset();
   saved_cursor_.reset();
   transaction_ = nullptr;
 }
 
 }  // namespace content