Updating custom element test to only load polyfill when needed.

Updating custom element test to only load polyfill when needed.

Also switching to a script element with a src, which I've found improves debuggability with some browsers.

BUG=13231
R=jmesserly@google.com

Committed: https://code.google.com/p/dart/source/detail?r=27456

[Jennifer Messerly, 2013-09-12 20:43:48]

lgtm

https://codereview.chromium.org/23647014/diff/1/pkg/custom_element/test/custo...
File pkg/custom_element/test/custom_element_test.dart (right):

https://codereview.chromium.org/23647014/diff/1/pkg/custom_element/test/custo...
pkg/custom_element/test/custom_element_test.dart:22: return script.onLoad.first;
Nice! This blocks the test until it loads? That was the bit I was missing, hence
used ".text" as a hacky workaround :)

Can enable CSP testing now with this fix?

[blois, 2013-09-12 21:23:13]

https://codereview.chromium.org/23647014/diff/1/pkg/custom_element/test/custo...
File pkg/custom_element/test/custom_element_test.dart (right):

https://codereview.chromium.org/23647014/diff/1/pkg/custom_element/test/custo...
pkg/custom_element/test/custom_element_test.dart:22: return script.onLoad.first;
On 2013/09/12 20:43:48, John Messerly wrote:
> Nice! This blocks the test until it loads? That was the bit I was missing,
hence
> used ".text" as a hacky workaround :)
> 
> Can enable CSP testing now with this fix?

The setUp function handles Future return types just like tests. Primary benefit
of this approach is that mutation_observer.js appears in your sources list and
makes it easier to navigate.

CSP does not allow programmatic insertion of script tags, so no.

[blois, 2013-09-12 22:24:17]

Committed patchset #1 manually as r27456 (presubmit successful).