Add support for providing an external file for extracting content.

components/dom_distiller/core/fake_distiller_page.cc

Index: components/dom_distiller/core/fake_distiller_page.cc
diff --git a/components/dom_distiller/core/fake_distiller_page.cc b/components/dom_distiller/core/fake_distiller_page.cc
index 208d3bb1800770a06b79b6427f4c2bb2a8a57c5b..50941083abcefda2ea44aa5a53d6d15f52a95378 100644
--- a/components/dom_distiller/core/fake_distiller_page.cc
+++ b/components/dom_distiller/core/fake_distiller_page.cc
@@ -12,7 +12,7 @@ MockDistillerPageFactory::MockDistillerPageFactory() {
 MockDistillerPageFactory::~MockDistillerPageFactory() {
 }
 
-MockDistillerPage::MockDistillerPage() {
+MockDistillerPage::MockDistillerPage() : DistillerPage("") {
 }
 MockDistillerPage::~MockDistillerPage() {
 }