Update viewport_meta setting on any navigation.

content/browser/frame_host/navigation_controller_impl.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 /*
  * Copyright (C) 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved.
  *     (http://www.torchmobile.com/)
  *
@@ skipping 785 matching lines @@
 
 bool NavigationControllerImpl::RendererDidNavigate(
     RenderFrameHostImpl* rfh,
     const FrameHostMsg_DidCommitProvisionalLoad_Params& params,
     LoadCommittedDetails* details,
     bool is_navigation_within_page,
     NavigationHandleImpl* navigation_handle) {
   is_initial_navigation_ = false;
 
   // Save the previous state before we clobber it.
+  bool overriding_user_agent_changed = false;
   if (GetLastCommittedEntry()) {
     details->previous_url = GetLastCommittedEntry()->GetURL();
     details->previous_entry_index = GetLastCommittedEntryIndex();
+    if (pending_entry_ &&

[Charlie Reis, 2017/01/12 17:45:59]

I don't think you can remove this check.  Plenty of navigations commit without a
pending entry (e.g., renderer-initiated navigations).

[aelias_OOO_until_Jul13, 2017/01/12 19:27:30]

Right, that removal was a text editing mistake, sorry.

+        pending_entry_->GetIsOverridingUserAgent() !=
+            GetLastCommittedEntry()->GetIsOverridingUserAgent())
+      overriding_user_agent_changed = true;
   } else {
     details->previous_url = GURL();
     details->previous_entry_index = -1;
   }
 
   // If there is a pending entry at this point, it should have a SiteInstance,
   // except for restored entries.
   DCHECK(pending_entry_index_ == -1 || pending_entry_->site_instance() ||
          pending_entry_->restore_type() != RestoreType::NONE);
   if (pending_entry_ && pending_entry_->restore_type() != RestoreType::NONE) {
@@ skipping 127 matching lines @@
   // we do not grant this entry additional bindings if we come back to it.
   active_entry->SetBindings(rfh->GetEnabledBindings());
 
   // Now prep the rest of the details for the notification and broadcast.
   details->entry = active_entry;
   details->is_main_frame = !rfh->GetParent();
   details->http_status_code = params.http_status_code;
 
   NotifyNavigationEntryCommitted(details);
 
+  if (overriding_user_agent_changed)
+    delegate_->UpdateOverridingUserAgent();
+
   // Update the nav_entry_id for each RenderFrameHost in the tree, so that each
   // one knows the latest NavigationEntry it is showing (whether it has
   // committed anything in this navigation or not). This allows things like
   // state and title updates from RenderFrames to apply to the latest relevant
   // NavigationEntry.
   int nav_entry_id = active_entry->GetUniqueID();
   for (FrameTreeNode* node : delegate_->GetFrameTree()->Nodes())
     node->current_frame_host()->set_nav_entry_id(nav_entry_id);
   return true;
 }
@@ skipping 1187 matching lines @@
     }
   }
 }
 
 void NavigationControllerImpl::SetGetTimestampCallbackForTest(
     const base::Callback<base::Time()>& get_timestamp_callback) {
   get_timestamp_callback_ = get_timestamp_callback;
 }
 
 }  // namespace content