[CI] Track total Compositing.{Browser,Renderer}.LayersUpdateTime

We current have a histogram for LayersUpdateTime but it is bucketed
by the layer count. This patch adds a new metric for the total
LayersUpdateTime that is not bucketed.

Bug: 825912
Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: Ie9d83f90abf529af97bc2393f8f3ad6dc2e3530d
Reviewed-on: https://chromium-review.googlesource.com/981262Reviewed-by: Majid Valipour <majidvp@chromium.org>
Reviewed-by: vmpstr <vmpstr@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Commit-Queue: vmpstr <vmpstr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#546208}

cc/trees/layer_tree_host.cc

@@ -18,6 +18,7 @@
 #include "base/command_line.h"
 #include "base/location.h"
 #include "base/memory/ptr_util.h"
+#include "base/metrics/histogram_functions.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/numerics/safe_math.h"
 #include "base/single_thread_task_runner.h"
@@ -670,12 +671,16 @@ bool LayerTreeHost::UpdateLayers() {
   micro_benchmark_controller_.DidUpdateLayers();
 
   if (const char* client_name = GetClientNameForMetrics()) {
+    auto elapsed = timer.Elapsed().InMicroseconds();
+
     std::string histogram_name =
-        base::StringPrintf("Compositing.%s.LayersUpdateTime.%d", client_name,
-                           GetLayersUpdateTimeHistogramBucket(NumLayers()));
-    base::Histogram::FactoryGet(histogram_name, 0, 10000000, 50,
-                                base::HistogramBase::kUmaTargetedHistogramFlag)
-        ->Add(timer.Elapsed().InMicroseconds());
+        base::StringPrintf("Compositing.%s.LayersUpdateTime", client_name);
+    base::UmaHistogramCounts10M(histogram_name, elapsed);
+
+    // Also add UpdateLayers metrics bucketed by the layer count.
+    base::StringAppendF(&histogram_name, ".%d",
+                        GetLayersUpdateTimeHistogramBucket(NumLayers()));
+    base::UmaHistogramCounts10M(histogram_name, elapsed);
   }
 
   return result;

tools/metrics/histograms/histograms.xml

@@ -10980,8 +10980,7 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
-<histogram base="true" name="Compositing.Browser.LayersUpdateTime"
-    units="microseconds">
+<histogram name="Compositing.Browser.LayersUpdateTime" units="microseconds">
   <owner>animations-dev@chromium.org</owner>
   <summary>
     Time spent updating layers, in microseconds. Recorded when layers are
@@ -11420,8 +11419,7 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
-<histogram base="true" name="Compositing.Renderer.LayersUpdateTime"
-    units="microseconds">
+<histogram name="Compositing.Renderer.LayersUpdateTime" units="microseconds">
   <owner>animations-dev@chromium.org</owner>
   <summary>
     Time spent updating layers, in microseconds. Recorded when layers are