Do not create unnecessary strings for each posted task

Reduces one of the hot spots in early startup.

Change-Id: I0fbf412a14cf1e31bbfe601d523fb8169fb73a99
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2523241
Commit-Queue: ssid <ssid@chromium.org>
Reviewed-by: François Doray <fdoray@chromium.org>
Cr-Commit-Position: refs/heads/master@{#825055}

base/critical_closure.h

@@ -8,6 +8,7 @@
 #include <utility>
 
 #include "base/callback.h"
+#include "base/location.h"
 #include "base/strings/string_piece.h"
 #include "build/build_config.h"
 
@@ -66,13 +67,25 @@ inline OnceClosure MakeCriticalClosure(StringPiece task_name,
       &internal::CriticalClosure::Run,
       Owned(new internal::CriticalClosure(task_name, std::move(closure))));
 }
+
+inline OnceClosure MakeCriticalClosure(const Location& posted_from,
+                                       OnceClosure closure) {
+  return MakeCriticalClosure(posted_from.ToString(), std::move(closure));
+}
+
 #else  // defined(OS_IOS)
 inline OnceClosure MakeCriticalClosure(StringPiece task_name,
                                        OnceClosure closure) {
   // No-op for platforms where the application does not need to acquire
   // background time for closures to finish when it goes into the background.
   return closure;
 }
+
+inline OnceClosure MakeCriticalClosure(const Location& posted_from,
+                                       OnceClosure closure) {
+  return closure;
+}
+
 #endif  // defined(OS_IOS)
 
 }  // namespace base

base/task/thread_pool/sequence.cc

@@ -45,8 +45,7 @@ void Sequence::Transaction::PushTask(Task task) {
 
   task.task = sequence()->traits_.shutdown_behavior() ==
                       TaskShutdownBehavior::BLOCK_SHUTDOWN
-                  ? MakeCriticalClosure(task.posted_from.ToString(),
-                                        std::move(task.task))
+                  ? MakeCriticalClosure(task.posted_from, std::move(task.task))
                   : std::move(task.task);
 
   if (sequence()->queue_.empty())