cc: Add more traces to checker imaging / image hijack code paths.

cc/playback/image_hijack_canvas.cc

Index: cc/playback/image_hijack_canvas.cc
diff --git a/cc/playback/image_hijack_canvas.cc b/cc/playback/image_hijack_canvas.cc
index bd26d3237c31fa9e9864a6317bcb6978344da80f..7fe112e9ae1954895ab978393de00431e6b1bdf6 100644
--- a/cc/playback/image_hijack_canvas.cc
+++ b/cc/playback/image_hijack_canvas.cc
@@ -5,6 +5,7 @@
 #include "cc/playback/image_hijack_canvas.h"
 
 #include "base/optional.h"
+#include "base/trace_event/trace_event.h"
 #include "cc/playback/discardable_image_map.h"
 #include "cc/tiles/image_decode_cache.h"
 #include "third_party/skia/include/core/SkPath.h"
@@ -137,6 +138,8 @@ ImageHijackCanvas::ImageHijackCanvas(int width,
 void ImageHijackCanvas::onDrawPicture(const SkPicture* picture,
                                       const SkMatrix* matrix,
                                       const SkPaint* paint) {
+  TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("cc.debug"),
+               "ImageHijackCanvas::onDrawPicture");
   // Ensure that pictures are unpacked by this canvas, instead of being
   // forwarded to the raster canvas.
   SkCanvas::onDrawPicture(picture, matrix, paint);
@@ -146,6 +149,8 @@ void ImageHijackCanvas::onDrawImage(const SkImage* image,
                                     SkScalar x,
                                     SkScalar y,
                                     const SkPaint* paint) {
+  TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("cc.debug"),
+               "ImageHijackCanvas::onDrawImage");
   if (!image->isLazyGenerated()) {
     DCHECK(!ShouldSkipImage(image));
     SkNWayCanvas::onDrawImage(image, x, y, paint);
@@ -184,6 +189,8 @@ void ImageHijackCanvas::onDrawImageRect(const SkImage* image,
                                         const SkRect& dst,
                                         const SkPaint* paint,
                                         SrcRectConstraint constraint) {
+  TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("cc.debug"),
+               "ImageHijackCanvas::onDrawImageRect");
   if (!image->isLazyGenerated()) {
     DCHECK(!ShouldSkipImage(image));
     SkNWayCanvas::onDrawImageRect(image, src, dst, paint, constraint);
@@ -225,6 +232,8 @@ void ImageHijackCanvas::onDrawImageRect(const SkImage* image,
 }
 
 void ImageHijackCanvas::onDrawRect(const SkRect& r, const SkPaint& paint) {
+  TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("cc.debug"),
+               "ImageHijackCanvas::onDrawRect");
   if (ShouldSkipImageInPaint(paint))
     return;
 
@@ -238,6 +247,8 @@ void ImageHijackCanvas::onDrawRect(const SkRect& r, const SkPaint& paint) {
 }
 
 void ImageHijackCanvas::onDrawPath(const SkPath& path, const SkPaint& paint) {
+  TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("cc.debug"),
+               "ImageHijackCanvas::onDrawPath");
   if (ShouldSkipImageInPaint(paint))
     return;
 
@@ -251,6 +262,8 @@ void ImageHijackCanvas::onDrawPath(const SkPath& path, const SkPaint& paint) {
 }
 
 void ImageHijackCanvas::onDrawOval(const SkRect& r, const SkPaint& paint) {
+  TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("cc.debug"),
+               "ImageHijackCanvas::onDrawOval");
   if (ShouldSkipImageInPaint(paint))
     return;
 
@@ -268,6 +281,8 @@ void ImageHijackCanvas::onDrawArc(const SkRect& r,
                                   SkScalar sweep_angle,
                                   bool use_center,
                                   const SkPaint& paint) {
+  TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("cc.debug"),
+               "ImageHijackCanvas::onDrawArc");
   if (ShouldSkipImageInPaint(paint))
     return;
 
@@ -282,6 +297,8 @@ void ImageHijackCanvas::onDrawArc(const SkRect& r,
 }
 
 void ImageHijackCanvas::onDrawRRect(const SkRRect& rr, const SkPaint& paint) {
+  TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("cc.debug"),
+               "ImageHijackCanvas::onDrawRRect");
   if (ShouldSkipImageInPaint(paint))
     return;
 
@@ -303,7 +320,12 @@ void ImageHijackCanvas::onDrawImageNine(const SkImage* image,
 }
 
 bool ImageHijackCanvas::ShouldSkipImage(const SkImage* image) const {
-  return images_to_skip_->find(image->uniqueID()) != images_to_skip_->end();
+  bool skip =
+      images_to_skip_->find(image->uniqueID()) != images_to_skip_->end();
+  TRACE_EVENT2(TRACE_DISABLED_BY_DEFAULT("cc.debug"),
+               "ImageHijackCanvas::ShouldSkipImage", "imageId",
+               image->uniqueID(), "skip", skip);
+  return skip;
 }
 
 bool ImageHijackCanvas::ShouldSkipImageInPaint(const SkPaint& paint) const {