I ran the test-suite (including SPEC 2006) in PGO mode comparing cold thresholds of 225 and 45. Here are some stats on the text size:
Out of 904 tests that ran, 197 see a change in text size. The average text size reduction (of all the 904 binaries) is 1.07%. Of the 197 binaries, 19 see a text size increase, as high as 18%, but most of them are small single source benchmarks. There are 3 multisource benchmarks with a >0.5% size increase (0.7, 1.3 and 2.1 are their % increases). On the other side of the spectrum, 31 benchmarks see >10% size reduction and 6 of them are MultiSource.
I haven't run the test-suite with other values of inlinecold-threshold. Since we have a cold callsite threshold of 45, I picked this value.