StatisticsExtension::GetCounters() has grown to repeat a lot of code
so to make it more maintainable and generate less machine code,
make it data driven. This makes a 64 bit Linux build 50 KB smaller.

Total change: -51677 bytes
==========================
  1 shrunk, for a net change of -51677 bytes (64222 bytes before, 12545 bytes after) across 1 sources
  279691 unchanged, totalling 51423668 bytes

Per-source Analysis:

-------------------------------------------------------------------------------------------------------------------
 -51677 - Source: /home/bratell/src/chromium/src/v8/src/extensions/statistics-extension.cc - (gained 0, lost 51677)
-------------------------------------------------------------------------------------------------------------------
  Shrunk symbols:
     -51677: v8::internal::StatisticsExtension::GetCounters(v8::FunctionCallbackInfo<v8::Value> const&) type=t, (was 64222 bytes, now 12545 bytes)

BUG=

Review URL: https://codereview.chromium.org/912413003

Cr-Commit-Position: refs/heads/master@{#26640}