Presubmit test for overriding properties generated by Polymer mixin shim

Presubmit test for overriding properties generated by Polymer mixin shim

Ensure we don't try to use an implementation detail of Polymer which could
break and is hacky.

With Polymer.useNativeCSSProperties enabled, Polymer uses custom properties to
shim mixins:
    :root {
      --paper-mixin {
        color: green;
        --paper-button-color: red;
      }
    }
    my-element
      @apply(--paper-mixin);
    }
becomes
    :root {
      --paper-mixin_-_color: green;
      --paper-mixin_-_paper-button-color: red;
    }
    my-element {
      color: var(--paper-mixin_-_color);
      --paper-button-color: var(--paper-mixin_-_paper-button-color);
    }

This happens at run-time, if custom variables are enabled, if the @apply shim
is used. Trying to change <my-element> my directly setting these variables:
    my-element {
      --paper-mixin_-_paper-button-color: blue; /* BAD */
    }
is unsafe.

R=dbeam@chromium.org

Committed: https://crrev.com/da606cedfa596f11a7e77a5197e86cdcd845500e
Cr-Commit-Position: refs/heads/master@{#413256}

[Dan Beam, 2016-08-19 20:49:12]

lgtm

[michaelpg, 2016-08-19 20:53:23]

The CQ bit was checked by michaelpg@chromium.org

[commit-bot: I haz the power, 2016-08-19 20:54:30]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-08-19 21:46:35]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-08-19 21:50:17]

Description was changed from

==========
Presubmit test for overriding properties generated by Polymer mixin shim

Ensure we don't try to use an implementation detail of Polymer which could
break and is hacky.

With Polymer.useNativeCSSProperties enabled, Polymer uses custom properties to
shim mixins:
    :root {
      --paper-mixin {
        color: green;
        --paper-button-color: red;
      }
    }
    my-element
      @apply(--paper-mixin);
    }
becomes
    :root {
      --paper-mixin_-_color: green;
      --paper-mixin_-_paper-button-color: red;
    }
    my-element {
      color: var(--paper-mixin_-_color);
      --paper-button-color: var(--paper-mixin_-_paper-button-color);
    }

This happens at run-time, if custom variables are enabled, if the @apply shim
is used. Trying to change <my-element> my directly setting these variables:
    my-element {
      --paper-mixin_-_paper-button-color: blue; /* BAD */
    }
is unsafe.

R=dbeam@chromium.org
==========

to

==========
Presubmit test for overriding properties generated by Polymer mixin shim

Ensure we don't try to use an implementation detail of Polymer which could
break and is hacky.

With Polymer.useNativeCSSProperties enabled, Polymer uses custom properties to
shim mixins:
    :root {
      --paper-mixin {
        color: green;
        --paper-button-color: red;
      }
    }
    my-element
      @apply(--paper-mixin);
    }
becomes
    :root {
      --paper-mixin_-_color: green;
      --paper-mixin_-_paper-button-color: red;
    }
    my-element {
      color: var(--paper-mixin_-_color);
      --paper-button-color: var(--paper-mixin_-_paper-button-color);
    }

This happens at run-time, if custom variables are enabled, if the @apply shim
is used. Trying to change <my-element> my directly setting these variables:
    my-element {
      --paper-mixin_-_paper-button-color: blue; /* BAD */
    }
is unsafe.

R=dbeam@chromium.org

Committed: https://crrev.com/da606cedfa596f11a7e77a5197e86cdcd845500e
Cr-Commit-Position: refs/heads/master@{#413256}
==========

[commit-bot: I haz the power, 2016-08-19 21:50:18]

Patchset 1 (id:??) landed as
https://crrev.com/da606cedfa596f11a7e77a5197e86cdcd845500e
Cr-Commit-Position: refs/heads/master@{#413256}