Feature/425 iframe navigation (#535)

* Updated navigation logic

* Fixed goroutine deadlock

* Fixed closing chan

* Added support of waiting for individual frame navigation

* Updated EventLoop API in order to avoid double closing of event sources

* Fixed attr retrieval

* Removed redundant println

* Updated DOM Readiness check

pkg/stdlib/html/find_frames.go

@@ -0,0 +1,58 @@
+package html
+
+import (
+	"context"
+	"github.com/MontFerret/ferret/pkg/drivers"
+	"github.com/MontFerret/ferret/pkg/runtime/core"
+	"github.com/MontFerret/ferret/pkg/runtime/values"
+)
+
+// FRAMES finds HTML frames by a given property selector.
+// Returns an empty array if frames not found.
+// @param page (HTMLPage) - HTML page.
+// @param prop (String) - Property selector.
+// @param value (Any) - Property value.
+// @returns (Array) - Returns an array of found HTML frames.
+func Frames(ctx context.Context, args ...core.Value) (core.Value, error) {
+	err := core.ValidateArgs(args, 3, 3)
+
+	if err != nil {
+		return values.None, err
+	}
+
+	page, err := drivers.ToPage(args[0])
+
+	if err != nil {
+		return values.None, err
+	}
+
+	frames, err := page.GetFrames(ctx)
+
+	if err != nil {
+		return values.None, err
+	}
+
+	propName := values.ToString(args[1])
+	propValue := args[2]
+
+	result, _ := frames.Find(func(value core.Value, idx int) bool {
+		doc, e := drivers.ToDocument(value)
+
+		if e != nil {
+			err = e
+			return false
+		}
+
+		currentPropValue, e := doc.GetIn(ctx, []core.Value{propName})
+
+		if e != nil {
+			err = e
+
+			return false
+		}
+
+		return currentPropValue.Compare(propValue) == 0
+	})
+
+	return result, err
+}