Add function to CancelableTaskTracker and convert BootTimeLoader (take 2)

This is the second try of: https://chromiumcodereview.appspot.com/11410073

Previous code has a potential race condition:

----------------------------------------------------------------
In old code when IsCanceledCallback is deleted. CancellationFlag is
deleted In task thread, and Untrack is called on client thread.

There's potential racy between:
1. CancellationFlag deletion. (task thread)
2. Untrack is called. (client thread)
3. TryCancel is called for the specific task. (client thread)

When the order is 1, 3, 2. There will be a CancellationFlag use after
delettion bug.
----------------------------------------------------------------

BUG=155883
TBR=brettw

Review URL: https://codereview.chromium.org/11414041

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@168321 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 14 insertions, 18 deletions

diff --git a/chrome/browser/chromeos/boot_times_loader.h b/chrome/browser/chromeos/boot_times_loader.h
index 691a44ff..dc420e8 100644
--- a/chrome/browser/chromeos/boot_times_loader.h
+++ b/chrome/browser/chromeos/boot_times_loader.h
@@ -12,7 +12,7 @@
 #include "base/callback_forward.h"
 #include "base/compiler_specific.h"
 #include "base/time.h"
-#include "chrome/browser/common/cancelable_request.h"
+#include "chrome/common/cancelable_task_tracker.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 #include "content/public/browser/render_widget_host.h"
@@ -22,17 +22,14 @@ namespace chromeos {
 // BootTimesLoader loads the bootimes of Chrome OS from the file system.
 // Loading is done asynchronously on the file thread. Once loaded,
 // BootTimesLoader calls back to a method of your choice with the boot times.
-// To use BootTimesLoader do the following:
+// To use BootTimesLoader, do the following:
 //
 // . In your class define a member field of type chromeos::BootTimesLoader and
-//   CancelableRequestConsumerBase.
+//   CancelableTaskTracker.
 // . Define the callback method, something like:
-//   void OnBootTimesLoader(chromeos::BootTimesLoader::Handle,
-//                             BootTimesLoader::BootTimes boot_times);
-// . When you want the version invoke: loader.GetBootTimes(&consumer, callback);
-class BootTimesLoader
-    : public CancelableRequestProvider,
-      public content::NotificationObserver {
+//   void OnBootTimesLoaded(const BootTimesLoader::BootTimes& boot_times);
+// . When you want the version invoke: loader.GetBootTimes(callback, &tracker_);
+class BootTimesLoader : public content::NotificationObserver {
  public:
   BootTimesLoader();
   virtual ~BootTimesLoader();
@@ -60,17 +57,14 @@ class BootTimesLoader
                   total(0) {}
   } BootTimes;
 
-  // Signature
-  typedef base::Callback<void(Handle, BootTimes)> GetBootTimesCallback;
-
-  typedef CancelableRequest<GetBootTimesCallback> GetBootTimesRequest;
-
   static BootTimesLoader* Get();
 
+  typedef base::Callback<void(const BootTimes&)> GetBootTimesCallback;
+
   // Asynchronously requests the info.
-  Handle GetBootTimes(
-      CancelableRequestConsumerBase* consumer,
-      const GetBootTimesCallback& callback);
+  CancelableTaskTracker::TaskId GetBootTimes(
+      const GetBootTimesCallback& callback,
+      CancelableTaskTracker* tracker);
 
   // Add a time marker for login. A timeline will be dumped to
   // /tmp/login-times-sent after login is done. If |send_to_uma| is true
@@ -119,7 +113,9 @@ class BootTimesLoader
    public:
     Backend() {}
 
-    void GetBootTimes(const scoped_refptr<GetBootTimesRequest>& request);
+    void GetBootTimesAndRunCallback(
+        const CancelableTaskTracker::IsCanceledCallback& is_canceled_cb,
+        const GetBootTimesCallback& callback);
 
    private:
     friend class base::RefCountedThreadSafe<Backend>;