Ignore viewport meta tags when Request Desktop Site is enabled.

content/browser/web_contents/web_contents_impl.cc

 // Copyright (c) 2012 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.
 
 #include "content/browser/web_contents/web_contents_impl.h"
 
 #include <stddef.h>
 
 #include <cmath>
 #include <utility>
@@ skipping 2153 matching lines @@
 }
 
 void WebContentsImpl::SetIsVirtualKeyboardRequested(bool requested) {
   virtual_keyboard_requested_ = requested;
 }
 
 bool WebContentsImpl::IsVirtualKeyboardRequested() {
   return virtual_keyboard_requested_;
 }
 
+bool WebContentsImpl::IsOverridingUserAgent() {
+  return GetController().GetVisibleEntry() &&
+         GetController().GetVisibleEntry()->GetIsOverridingUserAgent();
+}
+
 AccessibilityMode WebContentsImpl::GetAccessibilityMode() const {
   return accessibility_mode_;
 }
 
 void WebContentsImpl::AccessibilityEventReceived(
     const std::vector<AXEventNotificationDetails>& details) {
   FOR_EACH_OBSERVER(
       WebContentsObserver, observers_, AccessibilityEventReceived(details));
 }
 
@@ skipping 2656 matching lines @@
   }
   if (visible == should_normally_be_visible_)
     return;
 
   if (visible)
     WasShown();
   else
     WasHidden();
 }
 
+void WebContentsImpl::UpdateOverridingUserAgent() {
+  GetRenderViewHost()->OnWebkitPreferencesChanged();

[nasko, 2016/03/18 21:05:25]

This doesn't seem compatible with out-of-process iframes. The main frame will
use the proper user agent, but other processes rendering subframes will not.

You will need to call this method on each RenderViewHost that is in the list
found in the FrameTree object.

[aelias_OOO_until_Jul13, 2016/03/18 22:49:18]

The enableViewportMeta setting only ever has an effect on the main frame. 
Subframes ignore viewport meta tags by de-facto specification.  So I think
adding additional calls would be unnecessary complexity.

[nasko, 2016/03/25 23:29:05]

But this is method that calls for overriding user agent. It seems weird to use
different user agent strings on frames of the same page.

[aelias_OOO_until_Jul13, 2016/04/07 03:06:14]

OK, I changed to loop through the FrameTreeNodes (although the actual user agent
string doesn't need this to propagate, this just Update call only affects the
meta tag currently, but I suppose that might not always be the case).

+}
+
 void WebContentsImpl::SetJavaScriptDialogManagerForTesting(
     JavaScriptDialogManager* dialog_manager) {
   dialog_manager_ = dialog_manager;
 }
 
 }  // namespace content