Removing outdated usage of pending_navigation_params_.

Remaining usage of pending_navigation_params_ in renderer initiated
navigations where it is always false.

Bug: 789577
Change-Id: Ie8c214b01922f96f9bf3f8b5f6e6be4e82273bed
Reviewed-on: https://chromium-review.googlesource.com/1189804
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Commit-Queue: Arthur Hemery <ahemery@chromium.org>
Cr-Commit-Position: refs/heads/master@{#588801}

content/renderer/render_frame_impl.cc

@@ -6169,13 +6169,6 @@ WebNavigationPolicy RenderFrameImpl::DecidePolicyForNavigation(
         !weak_self) {
       return blink::kWebNavigationPolicyIgnore;
     }
-
-    // |navigation_start| must be recorded immediately after dispatching the
-    // beforeunload event.
-    if (pending_navigation_params_) {
-      pending_navigation_params_->common_params.navigation_start =
-          base::TimeTicks::Now();
-    }
   }
 
   // When an MHTML Archive is present, it should be used to serve iframe content