Remove embedded DartPads

[chalin]

Known affected pages:

• https://www.dartlang.org/guides/get-started
• https://www.dartlang.org/guides/language/language-tour
• https://www.dartlang.org/tutorials/language/futures
• https://www.dartlang.org/tutorials/language/streams

There may be more.

Chrome warnings as seen in the developer console:

• [Deprecation] Styling master document from stylesheets defined in HTML Imports is deprecated, and is planned to be removed in M65, around March 2018. Please refer to https://goo.gl/EGXzpw for possible migration paths.
• [Deprecation] /deep/ combinator is no longer supported in CSS dynamic profile. It is now effectively no-op, acting as if it were a descendant combinator. You should consider to remove it. See https://www.chromestatus.com/features/4964279606312960 for more details.
• Blink deferred a task in order to make scrolling smoother. Your timer and network tasks should take less than 50ms to run to avoid this. Please see https://developers.google.com/web/tools/chrome-devtools/profile/evaluate-performance/rail and https://crbug.com/574343#c40 for more information.

[kwalrath]

Is this caused by embedded DartPads?

[chalin]

Ah yes, that could very well be it!

[kwalrath]

I don't see the Blink warning when I view those pages in Chrome Canary: Version 64.0.3261.0 (Official Build) canary (64-bit).

[kwalrath]

DartPad's version of Polymer has been updated, but there are now 4 warnings in in https://www.dartlang.org/guides/get-started:

• [Deprecation] Styling master document from stylesheets defined in HTML Imports is deprecated, and is planned to be removed in M67, around May 2018. Please refer to https://goo.gl/EGXzpw for possible migration paths.
• imports.html:11890 This file is deprecated. Please use iron-flex-layout/iron-flex-layout-classes.html, and one of the specific dom-modules instead
• imports.html:12193 This file is deprecated. Please use iron-flex-layout/iron-flex-layout-classes.html, and one of the specific dom-modules instead
• [Deprecation] /deep/ combinator is no longer supported in CSS dynamic profile.It is now effectively no-op, acting as if it were a descendant combinator. /deep/ combinator will be removed, and will be invalid at M65. You should remove it. See https://www.chromestatus.com/features/4964279606312960 for more details.

For more info, see dart-lang/dart-pad#791.

[kwalrath]

Blocked on figuring out what our DartPad strategy will be.

/cc @RedBrogdon

[kwalrath]

#1799 switches us to the new DartPad, which causes no console warnings, yay!