Backport - easy fixes for memory leaks investigation
Bug 1234343 - Overly large values reported for gfx/heap-textures (changes size_t to ptrdiff_t (which "was fixed" from int32_t by previous bug) in FF46 (and Mozilla has closed related ticket with that confirmed bug as WORKSFORME for FF45, ugh Bug 1262088 - Incorrect about:memory reports (gfx/heap-textures) when playing HTML5 videos) Without it TBB shows
│ ├──3,155.00 MB (93.38%) ── heap-textures
(As heap-textures
causes a half of memory leaks, the helper ticket is worth tracking
Bug 1290100 - Decompose explicit/gfx/heap-textures)