Add UMA histograms for DirectComposition overlays.

gpu/ipc/service/direct_composition_surface_win.cc

Index: gpu/ipc/service/direct_composition_surface_win.cc
diff --git a/gpu/ipc/service/direct_composition_surface_win.cc b/gpu/ipc/service/direct_composition_surface_win.cc
index acbc271b0dd81360928050c87c9ecec203fc9e08..f97d720430ba88bd76580762a92da1f537177bb0 100644
--- a/gpu/ipc/service/direct_composition_surface_win.cc
+++ b/gpu/ipc/service/direct_composition_surface_win.cc
@@ -8,6 +8,7 @@
 #include <dcomptypes.h>
 
 #include "base/memory/ptr_util.h"
+#include "base/metrics/histogram_macros.h"
 #include "base/optional.h"
 #include "base/synchronization/waitable_event.h"
 #include "base/trace_event/trace_event.h"
@@ -344,6 +345,16 @@ void DCLayerTree::SwapChainPresenter::PresentToSwapChain(
   swap_chain_scale_y_ = bounds_rect.height() * 1.0f / swap_chain_size.height();
 
   swap_chain_->Present(first_present ? 0 : 1, 0);
+
+  base::win::ScopedComPtr<IDXGISwapChainMedia> swap_chain_media;
+  if (SUCCEEDED(swap_chain_.QueryInterface(swap_chain_media.Receive()))) {
+    DXGI_FRAME_STATISTICS_MEDIA stats = {};
+    if (SUCCEEDED(swap_chain_media->GetFrameStatisticsMedia(&stats))) {
+      UMA_HISTOGRAM_ENUMERATION(
+          "GPU.DirectComposition.CompositionMode", stats.CompositionMode,
+          DXGI_FRAME_PRESENTATION_MODE_COMPOSITION_FAILURE + 1);

[Ilya Sherman, 2017/03/29 05:16:42]

This code looks fragile, in the sense that someone who updates the enum won't
necessarily know to update this code.  Please add either a COUNT or a MAX entry
to the enum, and document that the enum is now being used to back an UMA
histogram, and should therefore be treated as append-only.

+    }
+  }
 }
 
 bool DCLayerTree::SwapChainPresenter::InitializeVideoProcessor(
@@ -555,6 +566,8 @@ void DCLayerTree::UpdateVisualClip(VisualInfo* visual_info,
 bool DCLayerTree::CommitAndClearPendingOverlays() {
   TRACE_EVENT1("gpu", "DCLayerTree::CommitAndClearPendingOverlays", "size",
                pending_overlays_.size());
+  UMA_HISTOGRAM_BOOLEAN("GPU.DirectComposition.OverlaysUsed",
+                        !pending_overlays_.empty());
   // Add an overlay with z-order 0 representing the main plane.
   gfx::Size surface_size = surface_->GetSize();
   pending_overlays_.push_back(base::MakeUnique<ui::DCRendererLayerParams>(