Check comparison tag before checking attributes in IfThenElseInstr::AttributesEqual.
Check comparison tag before checking attributes in IfThenElseInstr::AttributesEqual.

AttributesEqual must only be invoked on the instructions of the same type.

R=fschneider@google.com, rmacnak@google.com
BUG=http://dartbug.com/25422

Review URL: https://codereview.chromium.org/1586043005 .

dart-lang/sdk,dartino/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-lang/sdk,dartino/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk