port 411c5b7f (r32524)

  original commit message:
  Also remove the ResultMode from ToBooleanStub and always return true or
  false and use the same mechanism in fullcodegen.  This is in preparation
  for adding ToBoolean hints to TurboFan.

  Drive-by-fix: We can use the power of the ToBooleanIC in TurboFan now
  that the ResultMode is gone (and the runtime always returns true or
  false from the miss handler).

BUG=

Review URL: https://codereview.chromium.org/1500483002

Cr-Commit-Position: refs/heads/master@{#32543}