scheduler: Move the Blink scheduler into Blink

third_party/WebKit/public/platform/WebTaskRunner.h

Index: third_party/WebKit/public/platform/WebTaskRunner.h
diff --git a/third_party/WebKit/public/platform/WebTaskRunner.h b/third_party/WebKit/public/platform/WebTaskRunner.h
index 3f4c35c6096e2752606157dda14b886425c30bed..6e2bbd8e1647d3efd65dbe8562dcb11905a83621 100644
--- a/third_party/WebKit/public/platform/WebTaskRunner.h
+++ b/third_party/WebKit/public/platform/WebTaskRunner.h
@@ -13,8 +13,14 @@
 #include "wtf/Functional.h"
 #endif
 
+namespace base {
+class SingleThreadTaskRunner;
+}
+
 namespace blink {
 
+using SingleThreadTaskRunner = base::SingleThreadTaskRunner;
+
 // The blink representation of a chromium SingleThreadTaskRunner.
 class BLINK_PLATFORM_EXPORT WebTaskRunner {
 public:
@@ -59,6 +65,9 @@ public:
     // real time domain.
     virtual double monotonicallyIncreasingVirtualTimeSeconds() const = 0;
 
+    // Returns the underlying task runner object.
+    virtual SingleThreadTaskRunner* taskRunner() = 0;
+
 #ifdef INSIDE_BLINK
     // Helpers for posting bound functions as tasks.