Reland of (Set)IsOverridingUserAgent should be called on VisibleItem

ios/web/web_state/ui/crw_web_controller.mm

Index: ios/web/web_state/ui/crw_web_controller.mm
diff --git a/ios/web/web_state/ui/crw_web_controller.mm b/ios/web/web_state/ui/crw_web_controller.mm
index 6d0fb2cfa2b052059efebef06219a0dee45a6672..3564aabbfe50277e7ea23904b89f5f683b6b3132 100644
--- a/ios/web/web_state/ui/crw_web_controller.mm
+++ b/ios/web/web_state/ui/crw_web_controller.mm
@@ -458,9 +458,9 @@ @interface CRWWebController ()<CRWContextMenuDelegate,
 
 // Returns YES if the user interacted with the page recently.
 @property(nonatomic, readonly) BOOL userClickedRecently;
-// Returns whether the desktop user agent should be used when setting the user
-// agent.
-@property(nonatomic, readonly) BOOL useDesktopUserAgent;
+
+// Whether or not desktop user agent is used for the currentItem.
+@property(nonatomic, readonly) BOOL usesDesktopUserAgent;

[kkhorimoto, 2017/02/24 19:21:27]

Again, I think that it would be better to fold this logic directly into
|-webViewWithConfiguration:|.  The concept of a "current item" is going away in
the refactor, so exposing a property whose semantics are tightly knit with that
API is a bad idea.  When future users of the NavigationManager API need that
functionality, they will need to implement it themselves (and add a comment
explaining why that logic is needed, rather than using an existing
NavigationItem getter). Exposing it in a property like this invites misuse, as
someone working on this file in the future may use it without fully thinking
through whether the flag from the "current item" is needed.

[Eugene But (OOO till 7-30), 2017/02/24 19:49:18]

This is existing property which will be fully removed. There is no need to pass
self.usesDesktopUserAgent to BuildWKWebView, this logic is UIWebView cruft. With
UIWebView the only way to set UserAgent was changing NSUserDefaults before
UIWebView creation. WKWebView has API to set user agent, so there is no need to
recreate it when desktop UA is requested. I think we should leave this code as
it is because we will throw it away anyway.

 
 // Facade for Mojo API.
 @property(nonatomic, readonly) web::MojoFacade* mojoFacade;
@@ -2349,7 +2349,7 @@ - (BOOL)shouldClosePageOnNativeApplicationLoad {
   return rendererInitiatedWithoutInteraction || noNavigationItems;
 }
 
-- (BOOL)useDesktopUserAgent {
+- (BOOL)usesDesktopUserAgent {
   web::NavigationItem* item = [self currentNavItem];
   return item && item->IsOverridingUserAgent();
 }
@@ -4225,7 +4225,7 @@ - (WKWebView*)webViewWithConfiguration:(WKWebViewConfiguration*)config {
   // delegate must be specified.
   return web::BuildWKWebView(CGRectZero, config,
                              self.webStateImpl->GetBrowserState(),
-                             [self useDesktopUserAgent]);
+                             self.usesDesktopUserAgent);
 }
 
 - (void)setWebView:(WKWebView*)webView {