Called when an on-screen keyboard should be shown or hidden for the
specified |browser|. |input_mode| specifies what kind of keyboard should
be opened. If |input_mode| is CEF_TEXT_INPUT_MODE_NONE, any existing
keyboard for this browser should be hidden.
Called when an on-screen keyboard should be shown or hidden for the specified |browser|. |input_mode| specifies what kind of keyboard should be opened. If |input_mode| is CEF_TEXT_INPUT_MODE_NONE, any existing keyboard for this browser should be hidden.