Bug 1038038 (part 1) - Reduce ShapeTable::MIN_SIZE_LOG2. r=bhackett.

An entryCount of zero is common, due to initBoundFunction(), so it's worth
choosing a value that doesn't waste too much space in that case.

--HG--
extra : rebase_source : efcf627734d3b49eab58aaaebeff16458bb7d9ad
Bug 1038038 (part 2) - Compute sizeLog2 in ShapeTable::init() better. r=bhackett.

For exapmle, currently if you have an entryCount of 9 you end up with a
capacity of 32, when 16 would be more appropriate.

--HG--
extra : rebase_source : 300cd56c2dcbbb75ae54b227a5d1cab83c424a97
Bug 1038038 (part 3) - Increase ShapeTable::MIN_ENTRIES. r=bhackett.

A linear search of 15 items is likely to be competitive with a hash table
lookup.

--HG--
extra : rebase_source : b2e0cb690610aea8bd372b4fbc50c1cc7cd9e97e