[IMP] component: refactor rendering pipeline

This commit introduces a brand new rendering system based on a fiber
class and a scheduler.

closes #330

src/qweb/compilation_context.ts

@@ -22,6 +22,7 @@ export class CompilationContext {
   shouldDefineUtils: boolean = false;
   shouldDefineRefs: boolean = false;
   shouldDefineResult: boolean = true;
+  shouldDefineSibling: boolean = true;
   shouldProtectContext: boolean = false;
   shouldTrackScope: boolean = false;
   loopNumber: number = 0;
@@ -63,6 +64,9 @@ export class CompilationContext {
     if (this.shouldDefineResult) {
       this.code.unshift("    let result;");
     }
+    if (this.shouldDefineSibling) {
+      this.code.unshift("    let sibling = null;");
+    }
     if (this.shouldDefineRefs) {
       this.code.unshift("    context.__owl__.refs = context.__owl__.refs || {};");
     }

src/qweb/extensions.ts

@@ -207,9 +207,7 @@ QWeb.addDirective({
       `slot${slotKey}.call(this, context.__owl__.parent, Object.assign({}, extra, {parentNode: ${parentNode}, vars: extra.vars, parent: owner}));`
     );
     if (!ctx.parentNode) {
-      ctx.addLine(
-        `Promise.all(extra.promises).then(() => utils.defineProxy(result, ${parentNode}[0]))`
-      );
+      ctx.addLine(`utils.defineProxy(result, ${parentNode}[0]);`);
     }
     ctx.closeIf();
     return true;

src/qweb/qweb.ts

@@ -645,7 +645,7 @@ export class QWeb extends EventBus {
       if (name.startsWith("t-att-")) {
         let attName = name.slice(6);
         const v = ctx.getValue(value);
-        let formattedValue = typeof v === 'string' ? ctx.formatExpression(v) : v.id;
+        let formattedValue = typeof v === "string" ? ctx.formatExpression(v) : v.id;
 
         if (attName === "class") {
           ctx.rootContext.shouldDefineUtils = true;