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, 32 insertions, 25 deletions

diff --git a/chrome/browser/metrics/metrics_service.cc b/chrome/browser/metrics/metrics_service.cc
index 5839171..82cdeac 100644
--- a/chrome/browser/metrics/metrics_service.cc
+++ b/chrome/browser/metrics/metrics_service.cc
@@ -174,6 +174,7 @@
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/load_notification_details.h"
 #include "chrome/browser/memory_details.h"
+#include "chrome/browser/plugin_service.h"
 #include "chrome/browser/profile.h"
 #include "chrome/browser/renderer_host/render_process_host.h"
 #include "chrome/browser/search_engines/template_url_model.h"
@@ -284,35 +285,39 @@ class MetricsMemoryDetails : public MemoryDetails {
   DISALLOW_EVIL_CONSTRUCTORS(MetricsMemoryDetails);
 };
 
-class MetricsService::GetPluginListTaskComplete : public Task {
+// This object and its static functions manage the calls to and from
+// the plugin service.  It lives on the IO thread.  It only lives long
+// enough to handle the callback, then it deletes itself.
+class GetPluginListClient : public PluginService::GetPluginListClient {
  public:
-  explicit GetPluginListTaskComplete(
-      const std::vector<WebPluginInfo>& plugins) : plugins_(plugins) { }
-  virtual void Run() {
-    g_browser_process->metrics_service()->OnGetPluginListTaskComplete(plugins_);
+  // Call GetPluginList on a GetPluginListClient.  Used to proxy this call
+  // from the UI thread to the IO thread.
+  static void CallGetPluginList(GetPluginListClient* client) {
+    DCHECK(ChromeThread::CurrentlyOn(ChromeThread::IO));
+    PluginService::GetInstance()->GetPluginList(false, client);
   }
 
- private:
-  std::vector<WebPluginInfo> plugins_;
-};
-
-class MetricsService::GetPluginListTask : public Task {
- public:
-  explicit GetPluginListTask(MessageLoop* callback_loop)
-      : callback_loop_(callback_loop) {}
-
-  virtual void Run() {
-    std::vector<WebPluginInfo> plugins;
-    NPAPI::PluginList::Singleton()->GetPlugins(false, &plugins);
-
-    callback_loop_->PostTask(
-        FROM_HERE, new GetPluginListTaskComplete(plugins));
+  // Callback from the PluginService when the plugin list has been retrieved.
+  virtual void OnGetPluginList(const std::vector<WebPluginInfo>& plugins) {
+    DCHECK(ChromeThread::CurrentlyOn(ChromeThread::IO));
+    // Forward back to the UI thread.
+    ChromeThread::PostTask(
+        ChromeThread::UI, FROM_HERE,
+        NewRunnableFunction(&GetPluginListClient::GetPluginListComplete,
+                            plugins));
+    delete this;
   }
 
- private:
-  MessageLoop* callback_loop_;
+  // A function to proxy the plugin list back from the IO thread to the UI
+  // thread to call the metrics service.
+  // |plugins| is intentionally pass by value.
+  static void GetPluginListComplete(const std::vector<WebPluginInfo> plugins) {
+    DCHECK(ChromeThread::CurrentlyOn(ChromeThread::UI));
+    g_browser_process->metrics_service()->OnGetPluginListComplete(plugins);
+  }
 };
 
+
 // static
 void MetricsService::RegisterPrefs(PrefService* local_state) {
   DCHECK(IsSingleThreaded());
@@ -745,7 +750,7 @@ void MetricsService::InitializeMetricsState() {
   ScheduleNextStateSave();
 }
 
-void MetricsService::OnGetPluginListTaskComplete(
+void MetricsService::OnGetPluginListComplete(
     const std::vector<WebPluginInfo>& plugins) {
   DCHECK(state_ == PLUGIN_LIST_REQUESTED);
   plugins_ = plugins;
@@ -826,8 +831,10 @@ void MetricsService::StartRecording() {
 
     // Make sure the plugin list is loaded before the inital log is sent, so
     // that the main thread isn't blocked generating the list.
-    g_browser_process->file_thread()->message_loop()->PostDelayedTask(FROM_HERE,
-        new GetPluginListTask(MessageLoop::current()),
+    ChromeThread::PostDelayedTask(
+        ChromeThread::IO, FROM_HERE,
+        NewRunnableFunction(&GetPluginListClient::CallGetPluginList,
+                            new GetPluginListClient),
         kInitialInterlogDuration * 1000 / 2);
   }
 }