Relocate plugin list fetching to PluginService

We fetch the plugin list from three places.  Previously, each location had
custom code to proxy the query to the file thread.  This change moves
the query to the PluginService, which then internally manages posting to
the file thread and calling back.

I experimented with some different approaches to handling the lifetimes
of the requests and responses.  The approach now is simple:
- The PluginService plugin methods are called and respond on the IO
  thread.  Two of the three consumers of the plugin lists are already on
  the IO thread, so they don't need any complicated thread handling.
- None of the callers ever need to cancel their requests: one is a
  singleton, and the other two always wait (in terms of holding a ref
  on the object) for the requests to complete.  This makes lifetime
  management a lot simpler than it would otherwise be.

With this change in place, I can then look at refactoring the PluginService
implementation on Linux to do more complicated plugin loading as needed in
bug 17863.

BUG=17863

Review URL: http://codereview.chromium.org/437069

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@33344 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 13 insertions, 0 deletions

diff --git a/chrome/browser/plugin_service.h b/chrome/browser/plugin_service.h
index 7ab39e2..fba9b04 100644
--- a/chrome/browser/plugin_service.h
+++ b/chrome/browser/plugin_service.h
@@ -53,6 +53,19 @@ class PluginService
   void SetChromePluginDataDir(const FilePath& data_dir);
   const FilePath& GetChromePluginDataDir();
 
+  // An interface for GetPluginList callbacks.  Note that this is
+  // called directly by the PluginService on the IO thread, so the
+  // implementor of this interface must outlive the request.
+  class GetPluginListClient {
+   public:
+    // Called when the request completes.
+    virtual void OnGetPluginList(const std::vector<WebPluginInfo>& plugins) = 0;
+  };
+
+  // Start a query for the list of plugins.
+  // If |refresh| is true, refreshes the list.
+  void GetPluginList(bool refresh, GetPluginListClient* client);
+
   // Gets the browser's UI locale.
   const std::wstring& GetUILocale();