[MBI] Add GetCurrentAgentGroupScheduler to WebThreadScheduler

This CL adds GetCurrentAgentGroupScheduler function to WebThreadScheduler so that it can be called from the content layer.

Bug: 1105403, 1113102
Change-Id: I0c78867453bf942deb4dc98fd557ad4662d4a7e5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2444619
Commit-Queue: Minoru Chikamune <chikamune@chromium.org>
Reviewed-by: Alexander Timin <altimin@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Kouhei Ueno <kouhei@chromium.org>
Reviewed-by: Tal Pressman <talp@chromium.org>
Cr-Commit-Position: refs/heads/master@{#814060}

third_party/blink/public/platform/scheduler/test/web_fake_thread_scheduler.h

@@ -23,6 +23,7 @@ class WebFakeThreadScheduler : public WebThreadScheduler {
   scoped_refptr<base::SingleThreadTaskRunner> DefaultTaskRunner() override;
   scoped_refptr<base::SingleThreadTaskRunner> CompositorTaskRunner() override;
   std::unique_ptr<WebWidgetScheduler> CreateWidgetScheduler() override;
+  WebAgentGroupScheduler* GetCurrentAgentGroupScheduler() override;
   std::unique_ptr<WebRenderWidgetSchedulingState>
   NewRenderWidgetSchedulingState() override;
   void WillBeginFrame(const viz::BeginFrameArgs& args) override;

third_party/blink/public/platform/scheduler/test/web_mock_thread_scheduler.h

@@ -35,6 +35,7 @@ class WebMockThreadScheduler : public WebThreadScheduler {
   MOCK_METHOD0(LoadingTaskRunner,
                scoped_refptr<base::SingleThreadTaskRunner>());
   MOCK_METHOD0(IPCTaskRunner, scoped_refptr<base::SingleThreadTaskRunner>());
+  MOCK_METHOD0(GetCurrentAgentGroupScheduler, WebAgentGroupScheduler*());
   MOCK_METHOD0(NewRenderWidgetSchedulingState,
                std::unique_ptr<WebRenderWidgetSchedulingState>());
   MOCK_METHOD1(WillBeginFrame, void(const viz::BeginFrameArgs&));

third_party/blink/public/platform/scheduler/web_thread_scheduler.h

@@ -13,6 +13,7 @@
 #include "base/time/time.h"
 #include "build/build_config.h"
 #include "third_party/blink/public/common/input/web_input_event.h"
+#include "third_party/blink/public/platform/scheduler/web_agent_group_scheduler.h"
 #include "third_party/blink/public/platform/scheduler/web_rail_mode_observer.h"
 #include "third_party/blink/public/platform/scheduler/web_render_widget_scheduling_state.h"
 #include "third_party/blink/public/platform/web_common.h"
@@ -93,6 +94,16 @@ class BLINK_PLATFORM_EXPORT WebThreadScheduler {
   // thread.
   virtual std::unique_ptr<WebWidgetScheduler> CreateWidgetScheduler();
 
+  // Return the current active AgentGroupScheduler.
+  // When a task which belongs to a specific AgentGroupScheduler is going to be
+  // run, this AgentGroupScheduler becomes the current active
+  // AgentGroupScheduler. And when the task is finished, the current active
+  // AgentGroupScheduler becomes nullptr. So if there is no active
+  // AgentGroupScheduler, this function returns nullptr. This behaviour is
+  // implemented by MainThreadSchedulerImpl’s OnTaskStarted and OnTaskCompleted
+  // hook points. So you can’t use this functionality in task observers.
+  virtual WebAgentGroupScheduler* GetCurrentAgentGroupScheduler() = 0;
+
   // Returns a new WebRenderWidgetSchedulingState.  The signals from this will
   // be used to make scheduling decisions.
   virtual std::unique_ptr<WebRenderWidgetSchedulingState>

third_party/blink/renderer/platform/scheduler/common/dummy_schedulers.cc

@@ -252,6 +252,10 @@ class DummyWebThreadScheduler : public WebThreadScheduler,
       PageScheduler::Delegate*) override {
     return std::make_unique<DummyPageScheduler>();
   }
+
+  WebAgentGroupScheduler* GetCurrentAgentGroupScheduler() override {
+    return nullptr;
+  }
 };
 
 }  // namespace

third_party/blink/renderer/platform/scheduler/test/web_fake_thread_scheduler.cc

@@ -37,6 +37,11 @@ WebFakeThreadScheduler::CreateWidgetScheduler() {
   return std::make_unique<WebFakeWidgetScheduler>();
 }
 
+WebAgentGroupScheduler*
+WebFakeThreadScheduler::GetCurrentAgentGroupScheduler() {
+  return nullptr;
+}
+
 std::unique_ptr<WebRenderWidgetSchedulingState>
 WebFakeThreadScheduler::NewRenderWidgetSchedulingState() {
   return nullptr;