Add IPC message to open chrome://plugins from a missing plug-in placeholder.

chrome/renderer/plugins/blocked_plugin.h

Index: chrome/renderer/plugins/blocked_plugin.h
diff --git a/chrome/renderer/plugins/blocked_plugin.h b/chrome/renderer/plugins/blocked_plugin.h
index 597b5e78cf274a40044884c84ff02b0a8cd29755..f97673b08855b2cc7005943c95d861824102f8c4 100644
--- a/chrome/renderer/plugins/blocked_plugin.h
+++ b/chrome/renderer/plugins/blocked_plugin.h
@@ -59,9 +59,10 @@ class BlockedPlugin : public PluginPlaceholder {
   // Takes no arguments, and returns nothing.
   void HideCallback(const CppArgumentList& args, CppVariant* result);
 
-  // Opens a URL in a new tab.
-  // Takes one argument, a string specifying the URL to open. Returns nothing.
-  void OpenUrlCallback(const CppArgumentList& args, CppVariant* result);
+  // Opens chrome://plugins in a new tab.
+  // Takes no arguments, and returns nothing.
+  void OpenAboutPluginsCallback(const CppArgumentList& args,
+                                CppVariant* result);
 
   // Load the blocked plugin.
   void LoadPlugin();