feat(CssProcessor): add support for CssTransformers

Closes #860

modules/angular2/src/core/application.js

@@ -99,7 +99,7 @@ function _injectorBindings(appComponentType): List<Binding> {
       UrlResolver,
       StyleUrlResolver,
       StyleInliner,
-      CssProcessor,
+      bind(CssProcessor).toFactory(() => new CssProcessor(null), []),
   ];
 }
 

modules/angular2/src/core/compiler/css_processor.js

@@ -1,6 +1,7 @@
 import {DOM} from 'angular2/src/dom/dom_adapter';
 
 import {isPresent} from 'angular2/src/facade/lang';
+import {List} from 'angular2/src/facade/collection';
 
 import {CompileStep} from './pipeline/compile_step';
 import {CompileElement} from './pipeline/compile_element';
@@ -10,9 +11,16 @@ import {ShadowDomStrategy} from './shadow_dom_strategy';
 import {DirectiveMetadata} from './directive_metadata';
 
 /**
- * Processes the <style> tags during the compilation.
+ * Processes the <style> tags during the compilation:
+ * - Apply any given transformers,
+ * - Apply the shadow DOM strategy style step.
  */
 export class CssProcessor {
+  _transformers: List<CssTransformer>;
+
+  constructor(transformers: List<CssTransformer>) {
+    this._transformers = transformers;
+  }
 
   /**
    * Returns a compile step to be added to the compiler pipeline.
@@ -24,22 +32,35 @@ export class CssProcessor {
   getCompileStep(cmpMetadata: DirectiveMetadata, shadowDomStrategy: ShadowDomStrategy,
     templateUrl: string) {
     var strategyStep = shadowDomStrategy.getStyleCompileStep(cmpMetadata, templateUrl);
-    return new _CssProcessorStep(strategyStep);
+    return new _CssProcessorStep(strategyStep, this._transformers);
   }
 }
 
+export class CssTransformer {
+  transform(styleElement) {};
+}
+
 class _CssProcessorStep extends CompileStep {
   _strategyStep: CompileStep;
+  _transformers: List<CssTransformer>;
 
-  constructor(strategyStep: CompileStep) {
+  constructor(strategyStep: CompileStep, transformers: List<CssTransformer>) {
     super();
     this._strategyStep = strategyStep;
+    this._transformers = transformers;
   }
 
   process(parent:CompileElement, current:CompileElement, control:CompileControl) {
     if (DOM.tagName(current.element) == 'STYLE') {
       current.ignoreBindings = true;
 
+      if (isPresent(this._transformers)) {
+        var styleEl = current.element;
+        for (var i = 0; i < this._transformers.length; i++) {
+          this._transformers[i].transform(styleEl);
+        }
+      }
+
       if (isPresent(this._strategyStep)) {
         this._strategyStep.process(parent, current, control);
       }