VM-codegen: Prefer simpler is-check variant where possible

VM-codegen: Prefer simpler is-check variant where possible

Before we try anything more complex, check whether there
is only one class that satisfies an 'is' check. If so, we
can just check for that class id and deopt when new classes
are defined.  This change merely reverses the order of
existing code.

This is a reland of https://codereview.chromium.org/2899283002
after an unrelated bug that caused a crash was fixed at
https://github.com/dart-lang/sdk/issues/29774

R=kustermann@google.com, vegorov@google.com
BUG=

Committed: https://github.com/dart-lang/sdk/commit/b192ecfb24d973e700703dbaab336d55668ae804

[Vyacheslav Egorov (Google), 2017-06-23 10:58:49]

vegorov@google.com changed reviewers:
+ vegorov@google.com

[Vyacheslav Egorov (Google), 2017-06-23 10:58:50]

lgtm

[erikcorry, 2017-06-24 12:02:13]

Description was changed from

==========
VM-codegen: Prefer simpler is-check variant where possible

Before we try anything more complex, check whether there
is only one class that satisfies an 'is' check. If so, we
can just check for that class id and deopt when new classes
are defined.  This change merely reverses the order of
existing code.

This is a reland of https://codereview.chromium.org/2899283002
after an unrelated bug that caused a crash was fixed at
https://github.com/dart-lang/sdk/issues/29774

R=kustermann@google.com
BUG=
==========

to

==========
VM-codegen: Prefer simpler is-check variant where possible

Before we try anything more complex, check whether there
is only one class that satisfies an 'is' check. If so, we
can just check for that class id and deopt when new classes
are defined.  This change merely reverses the order of
existing code.

This is a reland of https://codereview.chromium.org/2899283002
after an unrelated bug that caused a crash was fixed at
https://github.com/dart-lang/sdk/issues/29774

R=kustermann@google.com, vegorov@google.com
BUG=

Committed:
https://github.com/dart-lang/sdk/commit/b192ecfb24d973e700703dbaab336d55668ae804
==========

[erikcorry, 2017-06-24 12:02:15]

Committed patchset #1 (id:1) manually as
b192ecfb24d973e700703dbaab336d55668ae804 (presubmit successful).