content, base, blink: remove the notion of blame contexts.

This change list is a part of a wider effort to remove
TRACE_EVENT_PHASE_(ENTER|LEAVE)_CONTEXT trace events
and associated instrumentation.

BUG=1349313

Change-Id: I8f7630e6dce858f32ba37a338fdac8067c3bd262
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3804884
Reviewed-by: Yutaka Hirano <yhirano@chromium.org>
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Commit-Queue: Yutaka Hirano <yhirano@chromium.org>
Reviewed-by: Alexander Timin <altimin@chromium.org>
Auto-Submit: Joseph Koshy <jkoshy@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1031316}

base/BUILD.gn

@@ -2366,8 +2366,6 @@ mixed_component("base") {
   if (enable_base_tracing) {
     sources += [
       "trace_event/auto_open_close_event.h",
-      "trace_event/blame_context.cc",
-      "trace_event/blame_context.h",
       "trace_event/builtin_categories.cc",
       "trace_event/builtin_categories.h",
       "trace_event/category_registry.cc",
@@ -3886,7 +3884,6 @@ test("base_unittests") {
   if (enable_base_tracing) {
     sources += [
       "test/trace_event_analyzer_unittest.cc",
-      "trace_event/blame_context_unittest.cc",
       "trace_event/event_name_filter_unittest.cc",
       "trace_event/heap_profiler_allocation_context_tracker_unittest.cc",
       "trace_event/memory_allocator_dump_unittest.cc",

base/task/sequence_manager/sequence_manager_impl_unittest.cc

@@ -3225,34 +3225,6 @@ TEST_P(SequenceManagerTest, CurrentlyExecutingTaskQueue_NestedLoop) {
   EXPECT_EQ(nullptr, sequence_manager()->currently_executing_task_queue());
 }
 
-#if BUILDFLAG(ENABLE_BASE_TRACING)
-TEST_P(SequenceManagerTest, BlameContextAttribution) {
-  if (GetUnderlyingRunnerType() == RunnerType::kMessagePump)
-    return;
-  using trace_analyzer::Query;
-
-  auto queue = CreateTaskQueue();
-
-  trace_analyzer::Start("*");
-  {
-    trace_event::BlameContext blame_context("base", "name", "type", "scope", 0,
-                                            nullptr);
-    blame_context.Initialize();
-    queue->SetBlameContext(&blame_context);
-    queue->task_runner()->PostTask(FROM_HERE, BindOnce(&NopTask));
-    RunLoop().RunUntilIdle();
-  }
-  auto analyzer = trace_analyzer::Stop();
-
-  trace_analyzer::TraceEventVector events;
-  Query q = Query::EventPhaseIs(TRACE_EVENT_PHASE_ENTER_CONTEXT) ||
-            Query::EventPhaseIs(TRACE_EVENT_PHASE_LEAVE_CONTEXT);
-  analyzer->FindEvents(q, &events);
-
-  EXPECT_EQ(2u, events.size());
-}
-#endif  // BUILDFLAG(ENABLE_BASE_TRACING)
-
 TEST_P(SequenceManagerTest, NoWakeUpsForCanceledDelayedTasks) {
   auto queue = CreateTaskQueue();
 

base/task/sequence_manager/task_queue.cc

@@ -180,7 +180,6 @@ void TaskQueue::ShutdownTaskQueue() {
     TakeTaskQueueImpl().reset();
     return;
   }
-  impl_->SetBlameContext(nullptr);
   sequence_manager_->UnregisterTaskQueueImpl(TakeTaskQueueImpl());
 }
 
@@ -272,13 +271,6 @@ void TaskQueue::RemoveTaskObserver(TaskObserver* task_observer) {
   impl_->RemoveTaskObserver(task_observer);
 }
 
-void TaskQueue::SetBlameContext(trace_event::BlameContext* blame_context) {
-  DCHECK_CALLED_ON_VALID_THREAD(associated_thread_->thread_checker);
-  if (!impl_)
-    return;
-  impl_->SetBlameContext(blame_context);
-}
-
 void TaskQueue::InsertFence(InsertFencePosition position) {
   DCHECK_CALLED_ON_VALID_THREAD(associated_thread_->thread_checker);
   if (!impl_)

base/task/sequence_manager/task_queue.h

@@ -28,10 +28,6 @@ namespace base {
 
 class TaskObserver;
 
-namespace trace_event {
-class BlameContext;
-}
-
 namespace sequence_manager {
 
 namespace internal {
@@ -302,11 +298,6 @@ class BASE_EXPORT TaskQueue : public RefCountedThreadSafe<TaskQueue> {
   void AddTaskObserver(TaskObserver* task_observer);
   void RemoveTaskObserver(TaskObserver* task_observer);
 
-  // Set the blame context which is entered and left while executing tasks from
-  // this task queue. |blame_context| must be null or outlive this task queue.
-  // Must be called on the thread this TaskQueue was created by.
-  void SetBlameContext(trace_event::BlameContext* blame_context);
-
   enum class InsertFencePosition {
     kNow,  // Tasks posted on the queue up till this point further may run.
            // All further tasks are blocked.

base/task/sequence_manager/task_queue_impl.cc

@@ -936,9 +936,6 @@ void TaskQueueImpl::NotifyWillProcessTask(const Task& task,
                                           bool was_blocked_or_low_priority) {
   DCHECK(should_notify_observers_);
 
-  if (main_thread_only().blame_context)
-    main_thread_only().blame_context->Enter();
-
   for (auto& observer : main_thread_only().task_observers)
     observer.WillProcessTask(task, was_blocked_or_low_priority);
 }
@@ -947,12 +944,6 @@ void TaskQueueImpl::NotifyDidProcessTask(const Task& task) {
   DCHECK(should_notify_observers_);
   for (auto& observer : main_thread_only().task_observers)
     observer.DidProcessTask(task);
-  if (main_thread_only().blame_context)
-    main_thread_only().blame_context->Leave();
-}
-
-void TaskQueueImpl::SetBlameContext(trace_event::BlameContext* blame_context) {
-  main_thread_only().blame_context = blame_context;
 }
 
 void TaskQueueImpl::InsertFence(TaskQueue::InsertFencePosition position) {

base/task/sequence_manager/task_queue_impl.h

@@ -141,7 +141,6 @@ class BASE_EXPORT TaskQueueImpl {
   TaskQueue::QueuePriority GetQueuePriority() const;
   void AddTaskObserver(TaskObserver* task_observer);
   void RemoveTaskObserver(TaskObserver* task_observer);
-  void SetBlameContext(trace_event::BlameContext* blame_context);
   void InsertFence(TaskQueue::InsertFencePosition position);
   void InsertFenceAt(TimeTicks time);
   void RemoveFence();
@@ -434,7 +433,6 @@ class BASE_EXPORT TaskQueueImpl {
     ObserverList<TaskObserver>::Unchecked task_observers;
     HeapHandle heap_handle;
     bool is_enabled = true;
-    raw_ptr<trace_event::BlameContext> blame_context = nullptr;  // Not owned.
     absl::optional<Fence> current_fence;
     absl::optional<TimeTicks> delayed_fence;
     // Snapshots the next sequence number when the queue is unblocked, otherwise

base/trace_event/base_tracing.h

@@ -15,7 +15,6 @@
 #if BUILDFLAG(ENABLE_BASE_TRACING)
 // Update the check in //base/PRESUBMIT.py when adding new headers here.
 // TODO(crbug/1006541): Switch to perfetto for trace event implementation.
-#include "base/trace_event/blame_context.h"               // nogncheck
 #include "base/trace_event/heap_profiler.h"               // nogncheck
 #include "base/trace_event/interned_args_helper.h"        // nogncheck
 #include "base/trace_event/memory_allocator_dump_guid.h"  // nogncheck

base/trace_event/base_tracing_forward.h

@@ -37,7 +37,6 @@ struct check_traced_value_support {
 namespace base {
 namespace trace_event {
 
-class BlameContext;
 class ConvertableToTraceFormat;
 class TracedValue;