Version: 55.0.2869.0
OS: Linux

Create a ColumnSet:

views::ColumnSet* column_set = layout->AddColumnSet(column_set_id);

column_set->AddColumn(views::GridLayout::FILL,
                      views::GridLayout::FILL,
                      1,
                      views::GridLayout::USE_PREF,
                      0,
                      kMinUsernameSize);

column_set->AddColumn(views::GridLayout::FILL,
                      views::GridLayout::FILL,
                      1,
                      views::GridLayout::USE_PREF,
                      0,
                      0);

Put a long text into the second column. The first column will basically disappear despite |kMinUsernameSize| was specified. It's used only if there is enough space.