[Autofill Assistant] Allow clicking on links.

Before this patch, navigation triggered by clicking on a link or through
javascript (renderer-initiated navigation) was considered an end state
for Autofill assistant.

With this patch, such actions are only considered an end state if the
page that's navigated to has no scripts. This is necessary, as such
navigation is part of the expected flow of some scripts.

Going back a page or refreshing through the UI (non renderer-initiated
navigation) are still considered an end state with this patch.

Bug: 806868
Change-Id: I5a38a82e7edf8b34a5830130b957dfad387e1b0d
Reviewed-on: https://chromium-review.googlesource.com/c/1329242Reviewed-by: Mathias Carlen <mcarlen@chromium.org>
Commit-Queue: Stephane Zermatten <szermatt@chromium.org>
Cr-Commit-Position: refs/heads/master@{#606826}

components/autofill_assistant/browser/controller.cc

@@ -360,12 +360,10 @@ void Controller::OnNoRunnableScriptsAnymore() {
   if (script_tracker_->running())
     return;
 
-  // We're on a page that has no scripts or the scripts have reached a state
-  // from which they cannot recover through a DOM change. This should never
-  // happen with a consistent set of scripts; there should always be an explicit
-  // end.
+  // We're navigated to a page that has no scripts or the scripts have reached a
+  // state from which they cannot recover through a DOM change.
   GetUiController()->ShowStatusMessage(
-      l10n_util::GetStringUTF8(IDS_AUTOFILL_ASSISTANT_DEFAULT_ERROR));
+      l10n_util::GetStringUTF8(IDS_AUTOFILL_ASSISTANT_GIVE_UP));
   GetUiController()->ShutdownGracefully();
   return;
 }
@@ -442,13 +440,18 @@ void Controller::DidStartNavigation(
   //  - server redirections, which might happen outside of a script, but
   //    because of a load triggered by a previously-running script.
   //  - same-document modifications, which might happen automatically
-  ///
-  // Everything else, such as clicking on a link, going back to a previous page,
-  // or refreshing the page is considered an end condition.
+  //  - javascript-initiated navigation or refresh
+  //  - navigation by clicking on a link
+  //  In the last two cases, autofill assistant might still give up later on if
+  //  it discovers that the new page has no scripts.
+  //
+  // Everything else, such as going back to a previous page, or refreshing the
+  // page is considered an end condition.
   if (navigation_handle->IsInMainFrame() &&
       web_contents()->GetLastCommittedURL().is_valid() &&
       !script_tracker_->running() && !navigation_handle->WasServerRedirect() &&
-      !navigation_handle->IsSameDocument()) {
+      !navigation_handle->IsSameDocument() &&
+      !navigation_handle->IsRendererInitiated()) {
     OnGiveUp();
     return;
   }