Ignore viewport meta tags when Request Desktop Site is enabled.

content/browser/web_contents/web_contents_impl.cc

Index: content/browser/web_contents/web_contents_impl.cc
diff --git a/content/browser/web_contents/web_contents_impl.cc b/content/browser/web_contents/web_contents_impl.cc
index 769812393ef8e9657bb5f044c4c3e61bc7e1c48d..a5091df5949e7c151d916ee4dd1cc2496c0809ea 100644
--- a/content/browser/web_contents/web_contents_impl.cc
+++ b/content/browser/web_contents/web_contents_impl.cc
@@ -2171,6 +2171,11 @@ bool WebContentsImpl::IsVirtualKeyboardRequested() {
   return virtual_keyboard_requested_;
 }
 
+bool WebContentsImpl::IsOverridingUserAgent() {
+  return GetController().GetVisibleEntry() &&
+         GetController().GetVisibleEntry()->GetIsOverridingUserAgent();
+}
+
 AccessibilityMode WebContentsImpl::GetAccessibilityMode() const {
   return accessibility_mode_;
 }
@@ -4847,6 +4852,10 @@ void WebContentsImpl::UpdateWebContentsVisibility(bool visible) {
     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;