Transmit a X-Chrome-UMA-Enabled bit to Google domains from clients that have UMA enabled.

chrome/browser/net/chrome_network_delegate.h

Index: chrome/browser/net/chrome_network_delegate.h
diff --git a/chrome/browser/net/chrome_network_delegate.h b/chrome/browser/net/chrome_network_delegate.h
index a582c388f1dfee223c44229f80cc69d40481944c..0bfc634b576ab5d26481c5a7fdf74037b8b27deb 100644
--- a/chrome/browser/net/chrome_network_delegate.h
+++ b/chrome/browser/net/chrome_network_delegate.h
@@ -27,26 +27,45 @@ class URLBlacklistManager;
 // add hooks into the network stack.
 class ChromeNetworkDelegate : public net::NetworkDelegate {
  public:
+  // The level of visibility of the browser window using this delegate. This
+  // determines if we are permitted to transmit certain bits of information or
+  // not.
+  enum BrowserVisibility {
+    NORMAL,
+    INCOGNITO,

[Ilya Sherman, 2012/04/19 18:52:59]

nit: I know it makes for longer lines, but perhaps BROWSER_VISIBILITY_NORMAL and
BROWSER_VISIBILITY_INCOGNITO would be clearer than just NORMAL when seen out of
the context of this header?

[SteveT, 2012/04/20 16:50:32]

Okay, okay. Done :)

+  };
+
   // If |profile| is NULL, events will be broadcasted to all profiles,
   // otherwise they will only be sent to the specified profile.
-  // |enable_referrers| should be initialized on the UI thread (see below)
-  // beforehand. This object's owner is responsible for cleaning it up at
-  // shutdown. If |cookie_settings| is NULL, all cookies are enabled,
-  // otherwise, the settings are enforced on all observed network requests.
+  // |enable_referrers| and |enable_metrics| should be initialized on the UI
+  // thread (see below) beforehand, though |enable_metrics| is optional and
+  // will be treated as false if not passed in. This object's owner is
+  // responsible for cleaning it up at shutdown. If |cookie_settings| is NULL,
+  // all cookies are enabled, otherwise, the settings are enforced on all
+  // observed network requests.
   ChromeNetworkDelegate(
       ExtensionEventRouterForwarder* event_router,
       ExtensionInfoMap* extension_info_map,
       const policy::URLBlacklistManager* url_blacklist_manager,
       void* profile,
       CookieSettings* cookie_settings,
-      BooleanPrefMember* enable_referrers);
+      BrowserVisibility visibility,
+      BooleanPrefMember* enable_referrers,
+      BooleanPrefMember* enable_metrics);
   virtual ~ChromeNetworkDelegate();
 
-  // Binds |enable_referrers| to |pref_service| and moves it to the IO thread.
-  // This method should be called on the UI thread.
+  // Binds |enable_referrers| to the kReferrersEnabled pref in |pref_service|
+  // and moves it to the IO thread. This method should be called on the UI
+  // thread.
   static void InitializeReferrersEnabled(BooleanPrefMember* enable_referrers,
                                          PrefService* pref_service);
 
+  // Binds |enable_referrers| to the kMetricsReportingEnabled pref in
+  // |pref_service| and moves it to the IO thread. This method should be called
+  // on the UI thread.
+  static void InitializeMetricsEnabled(BooleanPrefMember* enable_metrics,
+                                       PrefService* pref_service);
+
  private:
   // NetworkDelegate implementation.
   virtual int OnBeforeURLRequest(net::URLRequest* request,
@@ -83,16 +102,29 @@ class ChromeNetworkDelegate : public net::NetworkDelegate {
                             const std::string& cookie_line,
                             net::CookieOptions* options) OVERRIDE;
 
+  // Adds Chrome experiment and metrics state as custom headers to |headers|
+  // based on local state and |request|.
+  void AddChromeMetricsStateHeader(net::URLRequest* request,
+                                   net::HttpRequestHeaders* headers);
+
   scoped_refptr<ExtensionEventRouterForwarder> event_router_;
   void* profile_;
   scoped_refptr<CookieSettings> cookie_settings_;
 
+  // The visibility of the browser window that uses this delegate. Note that
+  // this field is not valid if |profile_| is NULL, so always check profile_
+  // first before this field.
+  BrowserVisibility visibility_;
+
   scoped_refptr<ExtensionInfoMap> extension_info_map_;
 
   // Weak, owned by our owner.
   BooleanPrefMember* enable_referrers_;
 
   // Weak, owned by our owner.
+  BooleanPrefMember* enable_metrics_;
+
+  // Weak, owned by our owner.
   const policy::URLBlacklistManager* url_blacklist_manager_;
 
   DISALLOW_COPY_AND_ASSIGN(ChromeNetworkDelegate);