Drop alert DCHECKs.

These DCHECKs don’t tell us anything other than that we fail to update
the browser-side notion of location when a document writes into an
about:blank document, but we know that.

BUG=820063,718570

Change-Id: I469d75afaafcd87c98529037a1fbbca155ce806c
Reviewed-on: https://chromium-review.googlesource.com/956282Reviewed-by: Nasko Oskov <nasko@chromium.org>
Commit-Queue: Avi Drissman <avi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#541989}

content/browser/frame_host/render_frame_host_impl.cc

@@ -2066,11 +2066,6 @@ void RenderFrameHostImpl::OnRunJavaScriptDialog(
   // process input events.
   GetProcess()->SetIgnoreInputEvents(true);
 
-  // TODO(nasko): It is strange to accept the frame URL as a parameter from
-  // the renderer. Investigate and remove parameter, but for now let's
-  // double check.
-  DCHECK_EQ(frame_url, last_committed_url_);
-
   delegate_->RunJavaScriptDialog(this, message, default_prompt, dialog_type,
                                  reply_msg);
 }
@@ -2082,11 +2077,6 @@ void RenderFrameHostImpl::OnRunBeforeUnloadConfirm(
   TRACE_EVENT1("navigation", "RenderFrameHostImpl::OnRunBeforeUnloadConfirm",
                "frame_tree_node", frame_tree_node_->frame_tree_node_id());
 
-  // TODO(nasko): It is strange to accept the frame URL as a parameter from
-  // the renderer. Investigate and remove parameter, but for now let's
-  // double check.
-  DCHECK_EQ(frame_url, last_committed_url_);
-
   // While a JS beforeunload dialog is showing, tabs in the same process
   // shouldn't process input events.
   GetProcess()->SetIgnoreInputEvents(true);