[Impeller] Add some traces around impeller rendering

flow/surface_frame.cc

@@ -35,6 +35,7 @@ SurfaceFrame::SurfaceFrame(sk_sp<SkSurface> surface,
 }
 
 bool SurfaceFrame::Submit() {
+  TRACE_EVENT0("flutter", "SurfaceFrame::Submit");
   if (submitted_) {
     return false;
   }

shell/common/rasterizer.cc

@@ -464,6 +464,7 @@ RasterStatus Rasterizer::DoDraw(
 RasterStatus Rasterizer::DrawToSurface(
     FrameTimingsRecorder& frame_timings_recorder,
     flutter::LayerTree& layer_tree) {
+  TRACE_EVENT0("flutter", "Rasterizer::DrawToSurface");
   FML_DCHECK(surface_);
 
   RasterStatus raster_status;

shell/gpu/gpu_surface_metal_impeller.mm

@@ -9,6 +9,7 @@
 
 #include "flutter/fml/make_copyable.h"
 #include "flutter/fml/mapping.h"
+#include "flutter/fml/trace_event.h"
 #include "flutter/impeller/display_list/display_list_dispatcher.h"
 #include "flutter/impeller/renderer/backend/metal/surface_mtl.h"
 
@@ -42,6 +43,8 @@
 
 // |Surface|
 std::unique_ptr<SurfaceFrame> GPUSurfaceMetalImpeller::AcquireFrame(const SkISize& frame_info) {
+  TRACE_EVENT0("impeller", "GPUSurfaceMetalImpeller::AcquireFrame");
+
   if (!IsValid()) {
     FML_LOG(ERROR) << "Metal surface was invalid.";
     return nullptr;

shell/platform/darwin/ios/framework/Source/FlutterPlatformViews.mm

@@ -586,6 +586,8 @@ - (BOOL)flt_hasFirstResponderInViewHierarchySubtree {
 bool FlutterPlatformViewsController::SubmitFrame(GrDirectContext* gr_context,
                                                  std::shared_ptr<IOSContext> ios_context,
                                                  std::unique_ptr<SurfaceFrame> frame) {
+  TRACE_EVENT0("flutter", "FlutterPlatformViewsController::SubmitFrame");
+
   // Any UIKit related code has to run on main thread.
   FML_DCHECK([[NSThread currentThread] isMainThread]);
   if (flutter_view_ == nullptr) {
@@ -600,8 +602,8 @@ - (BOOL)flt_hasFirstResponderInViewHierarchySubtree {
   // Resolve all pending GPU operations before allocating a new surface.
   background_canvas->flush();
 
-  // Clipping the background canvas before drawing the picture recorders requires to
-  // save and restore the clip context.
+  // Clipping the background canvas before drawing the picture recorders requires
+  // saving and restoring the clip context.
   SkAutoCanvasRestore save(background_canvas, /*doSave=*/true);
 
   // Maps a platform view id to a vector of `FlutterPlatformViewLayer`.