skia::AnalysisCanvas: implementation for IsCheapInRect().

cc/picture.cc

Index: cc/picture.cc
diff --git a/cc/picture.cc b/cc/picture.cc
index 1407f55dc4a1eb5ee470f302f155666abbec5b37..383637c7b1fbee8e89d28351b244bfd4c08e2cf6 100644
--- a/cc/picture.cc
+++ b/cc/picture.cc
@@ -6,6 +6,7 @@
 #include "cc/content_layer_client.h"
 #include "cc/picture.h"
 #include "cc/rendering_stats.h"
+#include "skia/ext/analysis_canvas.h"
 #include "third_party/skia/include/core/SkCanvas.h"
 #include "third_party/skia/include/core/SkData.h"
 #include "third_party/skia/include/core/SkTileGridPicture.h"
@@ -109,6 +110,19 @@ void Picture::Raster(
 }
 
 bool Picture::IsCheapInRect(const gfx::Rect& layer_rect) {

[Sami, 2013/02/04 10:57:54]

Should we make this a const method?

[Tom Hudson, 2013/02/05 17:02:00]

Done.

I also had to add contents_scale to the list of args so that the AnalysisCanvas
would line up with the real canvas in Raster().

+  skia::AnalysisCanvas canvas(gfx::RectToSkRect(layer_rect));
+  // If a picture has estimatd cost below this threshold, go ahead and
+  // wait until we have more pictures to draw (to amortize startup costs).
+  // If cost exceeds this threshold, start it now so we aren't blocked
+  // waiting for it.
+  // FIXME: Arbitrary number. Requires tuning & experimentation.
+  // Probably requires per-platform tuning; N10 average draw call takes
+  // 25x as long as Z620.
+  int pictureCostThreshold = 100;
+  canvas.drawPicture(*picture_);
+  if (canvas.getEstimatedCost() <= pictureCostThreshold) {

[nduca, 2013/02/04 10:34:33]

love this. convert this to bool isCheap() and push the threshold to analyscanvas
maybe? That way we dont have to instantiate a cc picture in order to unit test
it.

[Tom Hudson, 2013/02/05 17:02:00]

Done.

+    return true;
+  }
   return false;
 }