Record histogram of reason for quads not being put in an overlay.

cc/output/dc_layer_overlay.cc

Index: cc/output/dc_layer_overlay.cc
diff --git a/cc/output/dc_layer_overlay.cc b/cc/output/dc_layer_overlay.cc
index eda508e6e13243b6787f3c841565d0d0f0aa788c..c0adc39dc3ccb5436637aa5f27e351f2b5486130 100644
--- a/cc/output/dc_layer_overlay.cc
+++ b/cc/output/dc_layer_overlay.cc
@@ -4,6 +4,7 @@
 
 #include "cc/output/dc_layer_overlay.h"
 
+#include "base/metrics/histogram_macros.h"
 #include "cc/base/math_util.h"
 #include "cc/quads/solid_color_draw_quad.h"
 #include "cc/quads/yuv_video_draw_quad.h"
@@ -85,7 +86,7 @@ DCLayerOverlayProcessor::DCLayerResult DCLayerOverlayProcessor::FromDrawQuad(
   if (quad->shared_quad_state->blend_mode != SkBlendMode::kSrcOver)
     return DC_LAYER_FAILED_QUAD_BLEND_MODE;
 
-  DCLayerResult result = DC_LAYER_FAILED_UNKNOWN;
+  DCLayerResult result;
   switch (quad->material) {
     case DrawQuad::YUV_VIDEO_CONTENT:
       result =
@@ -93,7 +94,7 @@ DCLayerOverlayProcessor::DCLayerResult DCLayerOverlayProcessor::FromDrawQuad(
                       ca_layer_overlay);
       break;
     default:
-      return DC_LAYER_FAILED_UNKNOWN;
+      return DC_LAYER_FAILED_UNSUPPORTED_QUAD;
   }
   if (result != DC_LAYER_SUCCESS)
     return result;
@@ -128,13 +129,19 @@ void DCLayerOverlayProcessor::Process(ResourceProvider* resource_provider,
     DCLayerOverlay ca_layer;
     DCLayerResult result = FromDrawQuad(resource_provider, display_rect,
                                         quad_list->begin(), it, &ca_layer);
-    if (result != DC_LAYER_SUCCESS)
+    if (result != DC_LAYER_SUCCESS) {
+      UMA_HISTOGRAM_ENUMERATION("GPU.DirectComposition.DCLayerResult", result,
+                                DC_LAYER_FAILED_MAX);
       continue;
+    }
 
     if (!it->shared_quad_state->quad_to_target_transform
              .Preserves2dAxisAlignment() &&
         !base::FeatureList::IsEnabled(
             features::kDirectCompositionComplexOverlays)) {
+      UMA_HISTOGRAM_ENUMERATION("GPU.DirectComposition.DCLayerResult",
+                                DC_LAYER_FAILED_COMPLEX_TRANSFORM,
+                                DC_LAYER_FAILED_MAX);

[Ilya Sherman, 2017/05/24 23:52:49]

nit: The UMA_HISTOGRAM macros expand to a fair bit of code, so to help the
compiler avoid duplicating it, I'd recommend extracting out a small wrapper
function that you'd call like so:

  RecordDCLayerResult(DC_LAYER_FAILED_COMPLEX_TRANSFORM);

       continue;
     }
 
@@ -152,6 +159,8 @@ void DCLayerOverlayProcessor::Process(ResourceProvider* resource_provider,
       quad_list->EraseAndInvalidateAllPointers(it);
     } else if (!base::FeatureList::IsEnabled(
                    features::kDirectCompositionUnderlays)) {
+      UMA_HISTOGRAM_ENUMERATION("GPU.DirectComposition.DCLayerResult",
+                                DC_LAYER_FAILED_OCCLUDED, DC_LAYER_FAILED_MAX);
       continue;
     } else {
       // The quad is occluded, so replace it with a black solid color quad and