Have DumpPool return futures

Have DumpPool return futures when tasks are enqueued, instead of
having users register their task with a string. This change has the
following benefits:

* Simplifies DumpPool since it no longer needs to keep the map of
  strings to futures.

* Allows adding a set of tasks to DumpPool that might not be known at
  build time. For example, we can add a bunch of tasks from a vector,
  without needing to generate arbitrary strings for them.

* Reduces the ability to misuse DumpPool. Before this change, the user
  had to come up with strings representing each task, and needed to
  know a task with said name existed. This change moves it from being a
  runtime error to being a compile time one.

Test: atest dumpstate_smoke_test

Change-Id: Ic6c1a983b049e5236ac596e8af200a21c07ac31b
diff --git a/cmds/dumpstate/tests/dumpstate_test.cpp b/cmds/dumpstate/tests/dumpstate_test.cpp
index 42beb2b..70b4e5c 100644
--- a/cmds/dumpstate/tests/dumpstate_test.cpp
+++ b/cmds/dumpstate/tests/dumpstate_test.cpp
@@ -1720,14 +1720,13 @@
         dprintf(out_fd, "C");
     };
     setLogDuration(/* log_duration = */false);
-    dump_pool_->enqueueTaskWithFd(/* task_name = */"1", dump_func_1, std::placeholders::_1);
-    dump_pool_->enqueueTaskWithFd(/* task_name = */"2", dump_func_2, std::placeholders::_1);
-    dump_pool_->enqueueTaskWithFd(/* task_name = */"3", dump_func_3, std::placeholders::_1);
+    auto t1 = dump_pool_->enqueueTaskWithFd("", dump_func_1, std::placeholders::_1);
+    auto t2 = dump_pool_->enqueueTaskWithFd("", dump_func_2, std::placeholders::_1);
+    auto t3 = dump_pool_->enqueueTaskWithFd("", dump_func_3, std::placeholders::_1);
 
-    dump_pool_->waitForTask("1", "", out_fd_.get());
-    dump_pool_->waitForTask("2", "", out_fd_.get());
-    dump_pool_->waitForTask("3", "", out_fd_.get());
-    dump_pool_->shutdown();
+    WaitForTask(std::move(t1), "", out_fd_.get());
+    WaitForTask(std::move(t2), "", out_fd_.get());
+    WaitForTask(std::move(t3), "", out_fd_.get());
 
     std::string result;
     ReadFileToString(out_path_, &result);
@@ -1741,9 +1740,8 @@
         run_1 = true;
     };
 
-    dump_pool_->enqueueTask(/* task_name = */"1", dump_func_1);
-    dump_pool_->waitForTask("1", "", out_fd_.get());
-    dump_pool_->shutdown();
+    auto t1 = dump_pool_->enqueueTask(/* duration_title = */"1", dump_func_1);
+    WaitForTask(std::move(t1), "", out_fd_.get());
 
     std::string result;
     ReadFileToString(out_path_, &result);
@@ -1752,27 +1750,6 @@
     EXPECT_THAT(getTempFileCounts(kTestDataPath), Eq(0));
 }
 
-TEST_F(DumpPoolTest, Shutdown_withoutCrash) {
-    bool run_1 = false;
-    auto dump_func_1 = [&]() {
-        run_1 = true;
-    };
-    auto dump_func = []() {
-        sleep(1);
-    };
-
-    dump_pool_->start(/* thread_counts = */1);
-    dump_pool_->enqueueTask(/* task_name = */"1", dump_func_1);
-    dump_pool_->enqueueTask(/* task_name = */"2", dump_func);
-    dump_pool_->enqueueTask(/* task_name = */"3", dump_func);
-    dump_pool_->enqueueTask(/* task_name = */"4", dump_func);
-    dump_pool_->waitForTask("1", "", out_fd_.get());
-    dump_pool_->shutdown();
-
-    EXPECT_TRUE(run_1);
-    EXPECT_THAT(getTempFileCounts(kTestDataPath), Eq(0));
-}
-
 class TaskQueueTest : public DumpstateBaseTest {
 public:
     void SetUp() {