Add trace events to swap buffers (#2823)

sky/shell/gpu/direct/rasterizer_direct.cc

@@ -118,7 +118,11 @@ void RasterizerDirect::Draw(uint64_t layer_tree_ptr,
         compositor_context_.AcquireFrame(ganesh_canvas_.gr_context(), *canvas);
     canvas->clear(SK_ColorBLACK);
     layer_tree->Raster(frame);
-    canvas->flush();
+
+    {
+      TRACE_EVENT0("flutter", "SkCanvas::Flush");
+      canvas->flush();
+    }
 
     platform_view_->SwapBuffers();
   }

sky/shell/platform/android/platform_view_android.cc

@@ -13,11 +13,12 @@
 
 #include "base/bind.h"
 #include "base/location.h"
+#include "base/trace_event/trace_event.h"
 #include "jni/FlutterView_jni.h"
 #include "sky/engine/core/script/dart_service_isolate.h"
 #include "sky/engine/wtf/MakeUnique.h"
-#include "sky/shell/shell.h"
 #include "sky/shell/shell_view.h"
+#include "sky/shell/shell.h"
 
 namespace sky {
 namespace shell {
@@ -339,6 +340,7 @@ bool PlatformViewAndroid::ContextMakeCurrent() {
 }
 
 bool PlatformViewAndroid::SwapBuffers() {
+  TRACE_EVENT0("flutter", "PlatformViewAndroid::SwapBuffers");
   return context_ != nullptr ? context_->SwapBuffers() : false;
 }
 

sky/shell/platform/ios/platform_view_ios.mm

@@ -2,9 +2,11 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include "sky/shell/platform/ios/platform_view_ios.h"
+
 #include "base/mac/scoped_nsautorelease_pool.h"
+#include "base/trace_event/trace_event.h"
 #include "sky/engine/wtf/MakeUnique.h"
-#include "sky/shell/platform/ios/platform_view_ios.h"
 
 #import <OpenGLES/ES2/gl.h>
 #import <OpenGLES/ES2/glext.h>
@@ -284,6 +286,7 @@ bool PlatformViewIOS::ContextMakeCurrent() {
 }
 
 bool PlatformViewIOS::SwapBuffers() {
+  TRACE_EVENT0("flutter", "PlatformViewIOS::SwapBuffers");
   return context_ != nullptr ? context_->PresentRenderBuffer() : false;
 }
 

sky/shell/platform/mac/platform_view_mac.mm

@@ -6,6 +6,8 @@
 
 #include <AppKit/AppKit.h>
 
+#include "base/trace_event/trace_event.h"
+
 namespace sky {
 namespace shell {
 
@@ -42,6 +44,8 @@ bool PlatformViewMac::ContextMakeCurrent() {
 }
 
 bool PlatformViewMac::SwapBuffers() {
+  TRACE_EVENT0("flutter", "PlatformViewMac::SwapBuffers");
+
   if (!IsValid()) {
     return false;
   }