Reapply r21429 - Cleanup pending tasks under Valgrind as well.

base/message_loop.cc

Index: base/message_loop.cc
diff --git a/base/message_loop.cc b/base/message_loop.cc
index fbdc94f13d879a0b938ff4bdcb4a1282499e9d95..4c91b1ff23d423ffaf08d17a4ac6aec6a34d0233 100644
--- a/base/message_loop.cc
+++ b/base/message_loop.cc
@@ -372,10 +372,8 @@ bool MessageLoop::DeletePendingTasks() {
       // TODO(darin): Delete all tasks once it is safe to do so.
       // Until it is totally safe, just do it when running Purify or
       // Valgrind.
-#if defined(OS_WIN)
-#ifdef PURIFY
+#if defined(PURIFY)
       delete pending_task.task;
-#endif  // PURIFY
 #elif defined(OS_POSIX)
       if (RUNNING_ON_VALGRIND)
         delete pending_task.task;
@@ -385,14 +383,17 @@ bool MessageLoop::DeletePendingTasks() {
   did_work |= !deferred_non_nestable_work_queue_.empty();
   while (!deferred_non_nestable_work_queue_.empty()) {
     // TODO(darin): Delete all tasks once it is safe to do so.
-    // Until it is totaly safe, just delete them to keep purify happy.
-#ifdef PURIFY
-    Task* task = deferred_non_nestable_work_queue_.front().task;
+    // Until it is totaly safe, only delete them under Purify and Valgrind.
+    Task* task = NULL;
+#if defined(PURIFY)
+    task = deferred_non_nestable_work_queue_.front().task;
+#elif defined(OS_POSIX)
+    if (RUNNING_ON_VALGRIND)
+      task = deferred_non_nestable_work_queue_.front().task;
 #endif
     deferred_non_nestable_work_queue_.pop();
-#ifdef PURIFY
-    delete task;
-#endif
+    if (task)
+      delete task;
   }
   did_work |= !delayed_work_queue_.empty();
   while (!delayed_work_queue_.empty()) {