Revert of Add builders for tracing event's structural arguments

cc/resources/image_raster_worker_pool.h

Index: cc/resources/image_raster_worker_pool.h
diff --git a/cc/resources/image_raster_worker_pool.h b/cc/resources/image_raster_worker_pool.h
index 39ac7237266ced9c3a7c2c47d0ab31f1467abbd9..2e11a220f41da1ace4568978890687f974ea61f1 100644
--- a/cc/resources/image_raster_worker_pool.h
+++ b/cc/resources/image_raster_worker_pool.h
@@ -9,12 +9,6 @@
 #include "base/values.h"
 #include "cc/resources/raster_worker_pool.h"
 #include "cc/resources/rasterizer.h"
-
-namespace base {
-namespace debug {
-class ConvertableToTraceFormat;
-}
-}
 
 namespace cc {
 class ResourceProvider;
@@ -51,7 +45,7 @@
  private:
   void OnRasterFinished();
   void OnRasterRequiredForActivationFinished();
-  scoped_refptr<base::debug::ConvertableToTraceFormat> StateAsValue() const;
+  scoped_ptr<base::Value> StateAsValue() const;
 
   scoped_refptr<base::SequencedTaskRunner> task_runner_;
   TaskGraphRunner* task_graph_runner_;