Add cheapness predictor success histogram

cc/tile_manager.cc

Index: cc/tile_manager.cc
diff --git a/cc/tile_manager.cc b/cc/tile_manager.cc
index 2a426d35608af31d4ae3e9fcd7ff1bd4c3740e20..d1f4f1956431a542817b96c738ae10028eb64ec3 100644
--- a/cc/tile_manager.cc
+++ b/cc/tile_manager.cc
@@ -657,6 +657,7 @@ void TileManager::DispatchOneRasterTask(scoped_refptr<Tile> tile) {
                       resource_id),
                   tile->content_rect_,
                   tile->contents_scale(),
+                  use_cheapness_estimator_,
                   tile->picture_pile(),
                   &rendering_stats_);
     TileManager::OnRasterTaskCompleted(tile, resource.Pass(),
@@ -670,7 +671,8 @@ void TileManager::DispatchOneRasterTask(scoped_refptr<Tile> tile) {
                  resource_pool_->resource_provider()->mapPixelBuffer(
                      resource_id),
                  tile->content_rect_,
-                 tile->contents_scale()),
+                 tile->contents_scale(),
+                 use_cheapness_estimator_),
       base::Bind(&TileManager::OnRasterTaskCompletedByWorker,
                  base::Unretained(this),
                  tile,
@@ -776,6 +778,7 @@ void TileManager::DidTileBinChange(Tile* tile,
 void TileManager::RunRasterTask(uint8* buffer,
                                 const gfx::Rect& rect,
                                 float contents_scale,
+                                bool use_cheapness_estimator,
                                 PicturePileImpl* picture_pile,
                                 RenderingStats* stats) {
   TRACE_EVENT0("cc", "TileManager::RunRasterTask");
@@ -802,10 +805,43 @@ void TileManager::RunRasterTask(uint8* buffer,
       duration.InMilliseconds(),
       0, 10, 10
     );
+
+    if (use_cheapness_estimator)
+      RecordCheapnessPredictorCorrectness(
+        picture_pile->IsCheapInRect (rect, contents_scale),

[nduca, 2013/02/05 00:22:26]

might pull out the calculation into local vars so its clearer whats being
passed.

+        duration.InMillisecondsF() <= 1.0f
+      );
   }
 }
 
 // static
+void TileManager::RecordCheapnessPredictorCorrectness(

[nduca, 2013/02/05 00:22:26]

RecordCheapnessPredictorResults?

+    bool is_predicted_cheap,
+    bool is_actually_cheap) {
+ 
+  if (is_predicted_cheap)
+    UMA_HISTOGRAM_BOOLEAN(

[nduca, 2013/02/05 00:22:26]

i think these two should actually e

if (is_predicted_cheap && !is_actually_cheap)
   Renderer4.CheapPredictorWasBadlyWrong++
else (!is_predicted_cheap && is_actually_cheap)
   Renderer4.CheapPredictorWasOverconservative++

+      "Renderer4.CheapPredictorIsCheapAccuracy",
+      is_actually_cheap
+    );
+  else
+    UMA_HISTOGRAM_BOOLEAN(
+      "Renderer4.CheapPredictorIsNotCheapAccuracy",
+      !is_actually_cheap
+    );
+

[nduca, 2013/02/05 00:22:26]

are histograms the right thing to track here? The end state is that we want to
know "how many times did we estimate, and what % were right, what % were
overconservative, and what % were badly wrong?

To do that, I think you need a few more numbers than you're tracking here, like
# of times wrong.

+  bool is_correct_estimate = false;
+  if ((is_predicted_cheap && is_actually_cheap) ||

[nduca, 2013/02/05 00:22:26]

isn't this just 

is_predicted_cheap == is_actually_cheap?

+      (!is_predicted_cheap && !is_actually_cheap))
+    is_correct_estimate = true;
+
+  UMA_HISTOGRAM_BOOLEAN(
+    "Renderer4.CheapPredictorOverallAccuracy",

[nduca, 2013/02/05 00:22:26]

same comment about histograms being the right tool

+    is_correct_estimate
+  );
+}
+
+// static
 void TileManager::RunImageDecodeTask(skia::LazyPixelRef* pixel_ref,
                                      RenderingStats* stats) {
   TRACE_EVENT0("cc", "TileManager::RunImageDecodeTask");