Add a chrome://webapks page.

chrome/browser/android/webapps/webapp_registry.h

Index: chrome/browser/android/webapps/webapp_registry.h
diff --git a/chrome/browser/android/webapps/webapp_registry.h b/chrome/browser/android/webapps/webapp_registry.h
index 275271043115f0d10d5b7d959f4db1000edad6f2..a0326396ca48ddb3d843db45cd954a21e2fae4d2 100644
--- a/chrome/browser/android/webapps/webapp_registry.h
+++ b/chrome/browser/android/webapps/webapp_registry.h
@@ -5,6 +5,8 @@
 #ifndef CHROME_BROWSER_ANDROID_WEBAPPS_WEBAPP_REGISTRY_H_
 #define CHROME_BROWSER_ANDROID_WEBAPPS_WEBAPP_REGISTRY_H_
 
+#include <string>
+
 #include "base/callback_forward.h"
 #include "base/macros.h"
 
@@ -29,6 +31,12 @@ class WebappRegistry {
   virtual void ClearWebappHistoryForUrls(
       const base::Callback<bool(const GURL&)>& url_filter);
 
+  // Fetches a list of the Web APKs installed in the device, including their
+  // package name and version info.
+  virtual void ListWebAPKs(
+      const base::RepeatingCallback<void(std::string, std::string, int, int)>&
+          callback);
+
  private:
   DISALLOW_COPY_AND_ASSIGN(WebappRegistry);
 };