Revert "Add a shrinking reduction for dead continuation parameters."

Revert "Add a shrinking reduction for dead continuation parameters."

This reverts svn revision r43093, due to failures in dart2dart.  It
clashes with the commit just before it which has changed the type of
FunctionDefinition parameters.

Also, continuation eta-reduction can destroy a dead parameter
reduction.  In this case, it's not obvious which reduction we actually
want.  So though the fixes are simple, I will back this change out and
reevaluate it.

R=asgerf@google.com
BUG=

Committed: https://code.google.com/p/dart/source/detail?r=43105

[Kevin Millikin (Google), 2015-01-23 13:44:26]

I discussed this offline with Asger, and we'll just prohibit continuation
eta-reductions that turn a non-call continuation into a call continuation, for
now.

I'll still revert while making the fix.

[Kevin Millikin (Google), 2015-01-23 13:44:52]

Committed patchset #1 (id:1) manually as 43105 (presubmit successful).