Updating CustomElement lifecycle scope logic

Updating CustomElement lifecycle scope logic

More closely following what V8 is doing in:
https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit/Source/bindings/scripts/code_generator_v8.pm&l=1725

Primary issue was that this was being emitted in too many places (getters and attributes which didn't need it).

BUG=
R=vsm@google.com

Committed: https://code.google.com/p/dart/source/detail?r=28818

[vsm, 2013-10-03 16:20:41]

lgtm

https://chromiumcodereview.appspot.com/25675008/diff/1/tools/dom/scripts/syst...
File tools/dom/scripts/systemnative.py (right):

https://chromiumcodereview.appspot.com/25675008/diff/1/tools/dom/scripts/syst...
tools/dom/scripts/systemnative.py:795: if
generate_custom_element_scope_if_needed and
(ext_attrs.get('CustomElementCallbacks', 'None') != 'None' or 'Reflect' in
ext_attrs):
nit: line length

[blois, 2013-10-17 20:13:19]

Committed patchset #2 manually as r28818 (presubmit successful).