Add a histogram for tracking web store promo

chrome/browser/dom_ui/new_tab_ui.h

Index: chrome/browser/dom_ui/new_tab_ui.h
diff --git a/chrome/browser/dom_ui/new_tab_ui.h b/chrome/browser/dom_ui/new_tab_ui.h
index 35e2a87b1cb3c8b75dda3b8af6a8384afb5df074..58474e4474f37d660defce6e7d7c8044959bdb15 100644
--- a/chrome/browser/dom_ui/new_tab_ui.h
+++ b/chrome/browser/dom_ui/new_tab_ui.h
@@ -70,6 +70,18 @@ class NewTabUI : public DOMUI,
    private:
     virtual ~NewTabHTMLSource() {}
 
+    // Records a web store launch in the appropriate histograms. |promo_active|
+    // specifies if the web store promotion was active.
+    void RecordWebStoreLaunch(bool promo_active);
+
+    // Records an app launch in the appropriate histograms. |promo_active|
+    // specifies if the web store promotion was active.
+    void RecordAppLaunch(bool promo_active);
+
+    // Returns true if |path| indicates that the promotion is active, false if
+    // the promo is not active.
+    bool IsPromoActive(const std::string& path);
+
     // Whether this is the first run.
     static bool first_run_;