Record the time cost of deserializing all pending call stack profiles

Bug: 903972
Change-Id: Ib70702de4cda80970454fd5d8c296855673698cb
Reviewed-on: https://chromium-review.googlesource.com/c/1347145Reviewed-by: Mike Wittman <wittman@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Commit-Queue: Xi Cheng <chengx@chromium.org>
Cr-Commit-Position: refs/heads/master@{#611182}

components/metrics/call_stack_profile_metrics_provider.cc

@@ -9,10 +9,12 @@
 
 #include "base/bind.h"
 #include "base/macros.h"
+#include "base/metrics/histogram_macros.h"
 #include "base/no_destructor.h"
 #include "base/synchronization/lock.h"
 #include "base/thread_annotations.h"
 #include "base/time/time.h"
+#include "base/timer/elapsed_timer.h"
 #include "third_party/metrics_proto/chrome_user_metrics_extension.pb.h"
 
 namespace metrics {
@@ -113,6 +115,7 @@ std::vector<SampledProfile> PendingProfiles::RetrieveProfiles() {
   }
 
   // Deserialize all serialized profiles, skipping over any that fail to parse.
+  base::ElapsedTimer timer;
   std::vector<SampledProfile> profiles;
   profiles.reserve(serialized_profiles.size());
   for (const auto& serialized_profile : serialized_profiles) {
@@ -122,6 +125,8 @@ std::vector<SampledProfile> PendingProfiles::RetrieveProfiles() {
       profiles.push_back(std::move(profile));
     }
   }
+  UMA_HISTOGRAM_TIMES("StackSamplingProfiler.DeserializeAllPendingProfilesTime",
+                      timer.Elapsed());
 
   return profiles;
 }

tools/metrics/histograms/histograms.xml

@@ -106562,6 +106562,15 @@ uploading your change for review.
   </summary>
 </histogram>
 
+<histogram name="StackSamplingProfiler.DeserializeAllPendingProfilesTime"
+    units="ms" expires_after="2019-05-21">
+  <owner>chengx@chromium.org</owner>
+  <owner>wittman@chromium.org</owner>
+  <summary>
+    Amount of time taken to deserialize all pending call stack profiles.
+  </summary>
+</histogram>
+
 <histogram name="StackSamplingProfiler.ProfileDeserializationTime" units="ms"
     expires_after="2019-01-24">
   <obsolete>