Add support for providing an external file for extracting content.

components/dom_distiller/core/distiller_page.h

Index: components/dom_distiller/core/distiller_page.h
diff --git a/components/dom_distiller/core/distiller_page.h b/components/dom_distiller/core/distiller_page.h
index 74cf277935b81809bb979aae01e37bac2aa2a2d0..180b4ee17ccaa733f4dcec57bad7485303356ced 100644
--- a/components/dom_distiller/core/distiller_page.h
+++ b/components/dom_distiller/core/distiller_page.h
@@ -34,6 +34,11 @@ class DistillerPage {
            bool distillation_successful)> DistillerPageCallback;
 
   DistillerPage();
+  // Use this constructor to override the JS that comes packaged with Chrome.
+  // It should contain the string $$OPTIONS, which will be replaced with options
+  // passed in as proto::DomDistillerOptions before it is executed in the page
+  // context.
+  DistillerPage(std::string distiller_js_script);
   virtual ~DistillerPage();
 
   // Loads a URL. |OnDistillationDone| is called when the load completes or
@@ -57,6 +62,11 @@ class DistillerPage {
 
  private:
   bool ready_;
+  // Contains the script which will be injected into the page which is
+  // being distilled.  It should contain the string $$OPTIONS, which will be
+  // replaced with options passed in as proto::DomDistillerOptions before
+  // it is executed in the page context.
+  std::string distiller_js_script_;
   DistillerPageCallback distiller_page_callback_;
   DISALLOW_COPY_AND_ASSIGN(DistillerPage);
 };