gulp-polymer-css-build 
Statically apply Polymer's CSS Mixin shim and CSS Custom Property shim (future work) with the Polymer CSS Builder
Install
$ npm install --save-dev gulp-polymer-css-build
Usage
Single File with Shady DOM
const gulp = require('gulp');
const vulcanize = require('gulp-vulcanize');
const polymerCssBuild = require('gulp-polymer-css-build');
gulp.task('default', () =>
gulp.src('src/index.html')
.pipe(vulcanize({
abspath: '',
excludes: [],
stripExcludes: false
}))
.pipe(polymerCssBuild({
'build-for-shady': true
}))
.pipe(gulp.dest('dest'))
);
Single File with Shadow DOM
const gulp = require('gulp');
const vulcanize = require('gulp-vulcanize');
const polymerCssBuild = require('gulp-polymer-css-build');
gulp.task('default', () =>
gulp.src('src/index.html')
.pipe(vulcanize({
abspath: '',
excludes: [],
stripExcludes: false
}))
.pipe(polymerCssBuild())
.pipe(gulp.dest('dest'))
);
Multiple Files (shards) with Shady DOM
const gulp = require('gulp');
const wcs = require('gulp-web-component-shards');
const polymerCssBuild = require('gulp-polymer-css-build');
gulp.task('shards', () =>
gulp.src('src/**/*.html', { base: 'src', read: false })
.pipe(wcs({
root: 'src'
}))
.pipe(polymerCssBuild({
'build-for-shady': true
}))
.pipe(gulp.dest('dest'))
);
Multiple Files (shards) with Shadow DOM
const gulp = require('gulp');
const wcs = require('gulp-web-component-shards');
const polymerCssBuild = require('gulp-polymer-css-build');
gulp.task('shards', () =>
gulp.src('src/**/*.html', { base: 'src', read: false })
.pipe(wcs({
root: 'src'
}))
.pipe(polymerCssBuild())
.pipe(gulp.dest('dest'))
);
API
PolymerCssBuild([options])
See the polymer-css-build options.
License
MIT © John Riviello