Don't ping for extension blacklist when no extensions are installed....

chrome/browser/extensions/extensions_service.h

Index: chrome/browser/extensions/extensions_service.h
===================================================================
--- chrome/browser/extensions/extensions_service.h	(revision 33298)
+++ chrome/browser/extensions/extensions_service.h	(working copy)
@@ -51,6 +51,7 @@
                                       bool include_disabled) = 0;
   virtual void UpdateExtensionBlacklist(
     const std::vector<std::string>& blacklist) = 0;
+  virtual bool HasInstalledExtensions() = 0;
 };
 
 // Manages installed and running Chromium extensions.
@@ -88,6 +89,11 @@
     return &disabled_extensions_;
   }
 
+  // Returns true if any extensions are installed.
+  virtual bool HasInstalledExtensions() {
+    return !(extensions_.empty() && disabled_extensions_.empty());
+  }
+
   const FilePath& install_directory() const { return install_directory_; }
 
   // Initialize and start all installed extensions.