Remove unused Compositing.*.RasterTask.RasterPixelsPerMs2.* histograms

The histograms for number of pixels rastered per millisecond are not
looked at by anyone. Remove them.

R=enne@chromium.org

Bug: 955215
Change-Id: Id2d0fb0848888bedcc9177ed3b50ae36e3e7f803
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1579460
Commit-Queue: Stephen Chenney <schenney@chromium.org>
Reviewed-by: enne <enne@chromium.org>
Reviewed-by: Brian White <bcwhite@chromium.org>
Cr-Commit-Position: refs/heads/master@{#653605}
diff --git a/cc/tiles/tile_manager.cc b/cc/tiles/tile_manager.cc
index e797e6db..f5945a7 100644
--- a/cc/tiles/tile_manager.cc
+++ b/cc/tiles/tile_manager.cc
@@ -40,37 +40,6 @@
 // a tile is of solid color.
 const bool kUseColorEstimator = true;
 
-DEFINE_SCOPED_UMA_HISTOGRAM_AREA_TIMER(
-    ScopedSoftwareRasterTaskTimer,
-    "Compositing.%s.RasterTask.RasterUs.Software",
-    "Compositing.%s.RasterTask.RasterPixelsPerMs2.Software")
-
-DEFINE_SCOPED_UMA_HISTOGRAM_AREA_TIMER(
-    ScopedGpuRasterTaskTimer,
-    "Compositing.%s.RasterTask.RasterUs.Gpu",
-    "Compositing.%s.RasterTask.RasterPixelsPerMs2.Gpu")
-
-class ScopedRasterTaskTimer {
- public:
-  explicit ScopedRasterTaskTimer(bool use_gpu_rasterization) {
-    if (use_gpu_rasterization)
-      gpu_timer_.emplace();
-    else
-      software_timer_.emplace();
-  }
-
-  void SetArea(int area) {
-    if (software_timer_)
-      software_timer_->SetArea(area);
-    if (gpu_timer_)
-      gpu_timer_->SetArea(area);
-  }
-
- private:
-  base::Optional<ScopedSoftwareRasterTaskTimer> software_timer_;
-  base::Optional<ScopedGpuRasterTaskTimer> gpu_timer_;
-};
-
 // This class is wrapper for both ImageProvider and PaintWorkletImageProvider,
 // which is used in RasterSource::PlaybackSettings. It looks at the draw image
 // and decides which one of the two providers to dispatch the request to.
@@ -132,7 +101,6 @@
         tile_tracing_id_(static_cast<void*>(tile)),
         new_content_id_(tile->id()),
         source_frame_number_(tile->source_frame_number()),
-        is_gpu_rasterization_(is_gpu_rasterization),
         raster_buffer_(std::move(raster_buffer)),
         image_provider_(std::move(image_provider)),
         url_(std::move(url)) {
@@ -152,8 +120,6 @@
 
     frame_viewer_instrumentation::ScopedRasterTask raster_task(
         tile_tracing_id_, tile_resolution_, source_frame_number_, layer_id_);
-    ScopedRasterTaskTimer timer(is_gpu_rasterization_);
-    timer.SetArea(content_rect_.size().GetArea());
 
     DCHECK(raster_source_);
 
@@ -203,7 +169,6 @@
   void* tile_tracing_id_;
   uint64_t new_content_id_;
   int source_frame_number_;
-  bool is_gpu_rasterization_;
   std::unique_ptr<RasterBuffer> raster_buffer_;
   DispatchingImageProvider image_provider_;
   GURL url_;
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index 9c50ecd97..14a7c41b 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -17443,7 +17443,10 @@
 </histogram>
 
 <histogram name="Compositing.Browser.RasterTask.RasterPixelsPerMs2"
-    units="pixels/ms">
+    units="pixels/ms" expires_after="2019-4-24">
+  <obsolete>
+    Removed 04/2019. Was unused.
+  </obsolete>
   <owner>paint-dev@chromium.org</owner>
   <summary>
     Rasterized area, in pixels, divided by rasterization time, in milliseconds,
@@ -17963,7 +17966,10 @@
 </histogram>
 
 <histogram name="Compositing.Renderer.RasterTask.RasterPixelsPerMs2"
-    units="pixels/ms">
+    units="pixels/ms" expires_after="2019-4-24">
+  <obsolete>
+    Removed 04/2019. Was unused.
+  </obsolete>
   <owner>paint-dev@chromium.org</owner>
   <summary>
     Rasterized area, in pixels, divided by rasterization time, in milliseconds,