only call Stop when DistillerPageWebContents::CreateNewWebContents is…

… called. This maintains the original behavior from https://chromium.googlesource.com/chromium/src/+/fb688daf52cef3bb041634888583ee2c28c8af66%5E%21/components/dom_distiller/content/distiller_page_web_contents.cc without breaking sites that use the original webcontents

Fix brave/brave-browser#2991
Fix brave/brave-browser#2901

patches/components-dom_distiller-content-browser-distiller_page_web_contents.cc.patch

@@ -0,0 +1,14 @@
+diff --git a/components/dom_distiller/content/browser/distiller_page_web_contents.cc b/components/dom_distiller/content/browser/distiller_page_web_contents.cc
+index 9dd3a81fea2797c06db85868f0da94612b2a362d..9de2e23743c44deffafa96c7a2bdaabda046de87 100644
+--- a/components/dom_distiller/content/browser/distiller_page_web_contents.cc
++++ b/components/dom_distiller/content/browser/distiller_page_web_contents.cc
+@@ -182,7 +182,9 @@ void DistillerPageWebContents::ExecuteJavaScript() {
+   content::WebContentsObserver::Observe(nullptr);
+   // Stop any pending navigation since the intent is to distill the current
+   // page.
++  if (source_page_handle_->web_contents()->GetDelegate() == this)
+   source_page_handle_->web_contents()->Stop();
++
+   DVLOG(1) << "Beginning distillation";
+   RunIsolatedJavaScript(
+       frame, script_,