Expose sample_index argument through web ui (#412)
Expose sample_index argument through web ui (#412)

The option is exposed in the web ui's query string under a
new `?si=<sample_index>` parameter. This is particularly
useful for heap profiles, where switching between the four
indices (alloc_objects, alloc_space, inuse_objects, and inuse_space)
is a common task.

We could add a menu to the UI to make discovery of these
options easier, but for now this seems sufficient.
google/pprof,google/pprof,google/pprof,google/pprof