Adds a webstorePrivate method for silently installing extensions.

chrome/browser/extensions/crx_installer.cc

Index: chrome/browser/extensions/crx_installer.cc
diff --git a/chrome/browser/extensions/crx_installer.cc b/chrome/browser/extensions/crx_installer.cc
index a8b39ca53f00becbd1153ae22653a0c79497066a..c650daa409ea7fcfb7a679dcf673f825a0b467e7 100644
--- a/chrome/browser/extensions/crx_installer.cc
+++ b/chrome/browser/extensions/crx_installer.cc
@@ -58,7 +58,8 @@ static base::LazyInstance<Whitelist>
 }  // namespace
 
 CrxInstaller::WhitelistEntry::WhitelistEntry()
-  : use_app_installed_bubble(false) {}
+    : use_app_installed_bubble(false),
+      skip_post_install_ui(false) {}
 CrxInstaller::WhitelistEntry::~WhitelistEntry() {}
 
 // static
@@ -417,6 +418,8 @@ void CrxInstaller::ConfirmInstall() {
     whitelisted = true;
     if (entry->use_app_installed_bubble)
       client_->set_use_app_installed_bubble(true);
+    if (entry->skip_post_install_ui)
+      client_->set_skip_post_install_ui(true);
   }
 
   if (client_ &&