Eliminate unused function maps

Eliminate unused function maps

If a class contains more than 16 functions, the lookup works via a map rather than via a linear lookup in the functions array. If there are less than 16 functions, there is no need to allocate the map.

This saves about 240 maps and 7600 map entries in the core libraries alone.

BUG=
R=asiva@google.com

Committed: https://github.com/dart-lang/sdk/commit/72328eaf934d6ebf6ce60af40b0ac6b75e9f519b

[hausner, 2015-10-15 00:06:25]

hausner@google.com changed reviewers:
+ asiva@google.com

[hausner, 2015-10-15 00:07:07]

Not sure whether the snapshot size is smaller, too. Would be nice.

[siva, 2015-10-15 01:13:15]

LGTM with one comment.

https://codereview.chromium.org/1410443003/diff/1/runtime/vm/object.cc
File runtime/vm/object.cc (right):

https://codereview.chromium.org/1410443003/diff/1/runtime/vm/object.cc#newcod...
runtime/vm/object.cc:2213: }
Not sure who uses this function but shouldn't this function now set the hash
table back to NULL here as we might transition from kFunctionLookupHashTreshold
to kFunctionLookupHashTreshold - 1 and end up missing the reset of the hash
table as it is conditional now.

[hausner, 2015-10-15 17:08:24]

Committed patchset #2 (id:20001) manually as
72328eaf934d6ebf6ce60af40b0ac6b75e9f519b (presubmit successful).