perf ui browser: Allow overriding refresh_dimensions method

perf ui browser: Allow overriding refresh_dimensions method

Some browsers, like the hist_browser, may want to be notified everytime
a refresh_dimensions is needed, so that it can reset ui_browser->rows,
for instance, or do some other related reaction to screen resizings.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-ielvluuemzn30bneh0zk3twi@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>