1 files changed, 31 insertions, 7 deletions

diff --git a/chromium/base/task/task_traits.h b/chromium/base/task/task_traits.h
index c1e52ed0f07..03abf17913f 100644
--- a/chromium/base/task/task_traits.h
+++ b/chromium/base/task/task_traits.h
@@ -185,6 +185,14 @@ struct WithBaseSyncPrimitives {};
 // between tasks, see base::PostTask::CreateSequencedTaskRunner.
 struct ThreadPool {};
 
+// Tasks and task runners with this thread will run tasks on the virtual thread
+// (sequence) they are posted/created from. Other traits may be specified
+// alongside this one to refine properties for the associated tasks
+// (e.g. base::TaskPriority or content::BrowserTaskType) as long as those traits
+// are compatible with the current thread (e.g. cannot specify base::MayBlock()
+// on a non-blocking thread or alter base::TaskShutdownBehavior).
+struct CurrentThread {};
+
 // Describes metadata for a single task or a group of tasks.
 class BASE_EXPORT TaskTraits {
  public:
@@ -196,6 +204,7 @@ class BASE_EXPORT TaskTraits {
     ValidTrait(MayBlock);
     ValidTrait(WithBaseSyncPrimitives);
     ValidTrait(ThreadPool);
+    ValidTrait(CurrentThread);
   };
 
   // Invoking this constructor without arguments produces TaskTraits that are
@@ -255,15 +264,22 @@ class BASE_EXPORT TaskTraits {
         may_block_(trait_helpers::HasTrait<MayBlock, ArgTypes...>()),
         with_base_sync_primitives_(
             trait_helpers::HasTrait<WithBaseSyncPrimitives, ArgTypes...>()),
-        use_thread_pool_(trait_helpers::HasTrait<ThreadPool, ArgTypes...>()) {
+        use_thread_pool_(trait_helpers::HasTrait<ThreadPool, ArgTypes...>()),
+        use_current_thread_(
+            trait_helpers::HasTrait<CurrentThread, ArgTypes...>()) {
     constexpr bool has_thread_pool =
         trait_helpers::HasTrait<ThreadPool, ArgTypes...>();
     constexpr bool has_extension =
         !trait_helpers::AreValidTraits<ValidTrait, ArgTypes...>::value;
+    constexpr bool has_current_thread =
+        trait_helpers::HasTrait<CurrentThread, ArgTypes...>();
+    static_assert(
+        !has_current_thread || !has_thread_pool,
+        "base::CurrentThread is mutually exclusive with base::ThreadPool");
     static_assert(
-        has_thread_pool ^ has_extension,
+        has_thread_pool ^ has_extension || has_current_thread,
         "Traits must explicitly specify a destination (e.g. ThreadPool or a "
-        "named thread like BrowserThread)");
+        "named thread like BrowserThread, or CurrentThread)");
   }
 
   constexpr TaskTraits(const TaskTraits& other) = default;
@@ -271,14 +287,15 @@ class BASE_EXPORT TaskTraits {
 
   // TODO(eseckler): Default the comparison operator once C++20 arrives.
   bool operator==(const TaskTraits& other) const {
-    static_assert(sizeof(TaskTraits) == 15,
+    static_assert(sizeof(TaskTraits) == 16,
                   "Update comparison operator when TaskTraits change");
     return extension_ == other.extension_ && priority_ == other.priority_ &&
            shutdown_behavior_ == other.shutdown_behavior_ &&
            thread_policy_ == other.thread_policy_ &&
            may_block_ == other.may_block_ &&
            with_base_sync_primitives_ == other.with_base_sync_primitives_ &&
-           use_thread_pool_ == other.use_thread_pool_;
+           use_thread_pool_ == other.use_thread_pool_ &&
+           use_current_thread_ == other.use_current_thread_;
   }
 
   // Sets the priority of tasks with these traits to |priority|.
@@ -335,6 +352,10 @@ class BASE_EXPORT TaskTraits {
   // Returns true if tasks with these traits execute on the thread pool.
   constexpr bool use_thread_pool() const { return use_thread_pool_; }
 
+  // Returns true if tasks with these traits execute on the virtual thread
+  // (sequence) they are posted/created from.
+  constexpr bool use_current_thread() const { return use_current_thread_; }
+
   uint8_t extension_id() const { return extension_.extension_id; }
 
   // Access the extension data by parsing it into the provided extension type.
@@ -353,6 +374,7 @@ class BASE_EXPORT TaskTraits {
              TaskPriority priority,
              bool may_block,
              bool use_thread_pool,
+             bool use_current_thread,
              TaskTraitsExtensionStorage extension)
       : extension_(extension),
         priority_(static_cast<uint8_t>(priority) |
@@ -362,8 +384,9 @@ class BASE_EXPORT TaskTraits {
         thread_policy_(static_cast<uint8_t>(ThreadPolicy::PREFER_BACKGROUND)),
         may_block_(may_block),
         with_base_sync_primitives_(false),
-        use_thread_pool_(use_thread_pool) {
-    static_assert(sizeof(TaskTraits) == 15, "Keep this constructor up to date");
+        use_thread_pool_(use_thread_pool),
+        use_current_thread_(use_current_thread) {
+    static_assert(sizeof(TaskTraits) == 16, "Keep this constructor up to date");
   }
 
   // This bit is set in |priority_|, |shutdown_behavior_| and |thread_policy_|
@@ -378,6 +401,7 @@ class BASE_EXPORT TaskTraits {
   bool may_block_;
   bool with_base_sync_primitives_;
   bool use_thread_pool_;
+  bool use_current_thread_;
 };
 
 // Returns string literals for the enums defined in this file. These methods