Retire call stack profile serialization/deserialization metrics

StackSamplingProfiler.ProfileDeserializationTime is recorded for every
profile to deserialize, which can be expensive when a lot of profiles
are pending upload. Since we have already got enough data for these
metrics, we should retire them.

Bug: 851163
Change-Id: I703e8b01752832d9574e804b1a28c2a2bfd0058e
Reviewed-on: https://chromium-review.googlesource.com/c/1332772
Commit-Queue: Xi Cheng <chengx@chromium.org>
Reviewed-by: Mike Wittman <wittman@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#607450}

components/metrics/call_stack_profile_metrics_provider.cc

@@ -9,12 +9,10 @@
 
 #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 {
@@ -117,12 +115,9 @@ std::vector<SampledProfile> PendingProfiles::RetrieveProfiles() {
   std::vector<SampledProfile> profiles;
   profiles.reserve(serialized_profiles.size());
   for (const auto& serialized_profile : serialized_profiles) {
-    base::ElapsedTimer timer;
     SampledProfile profile;
     if (profile.ParseFromArray(serialized_profile.data(),
                                serialized_profile.size())) {
-      UMA_HISTOGRAM_TIMES("StackSamplingProfiler.ProfileDeserializationTime",
-                          timer.Elapsed());
       profiles.push_back(std::move(profile));
     }
   }
@@ -180,11 +175,8 @@ void PendingProfiles::MaybeCollectProfile(base::TimeTicks profile_start_time,
   }
 
   // Serialize the profile without holding the lock.
-  base::ElapsedTimer timer;
   std::string serialized_profile;
   profile.SerializeToString(&serialized_profile);
-  UMA_HISTOGRAM_TIMES("StackSamplingProfiler.ProfileSerializationTime",
-                      timer.Elapsed());
 
   MaybeCollectSerializedProfile(profile_start_time,
                                 std::move(serialized_profile));

tools/metrics/histograms/histograms.xml

@@ -105462,6 +105462,9 @@ uploading your change for review.
 
 <histogram name="StackSamplingProfiler.ProfileDeserializationTime" units="ms"
     expires_after="2019-01-24">
+  <obsolete>
+    Removed 11/2018 as we no longer record this metric.
+  </obsolete>
   <owner>chengx@chromium.org</owner>
   <owner>wittman@chromium.org</owner>
   <summary>
@@ -105471,6 +105474,9 @@ uploading your change for review.
 
 <histogram name="StackSamplingProfiler.ProfileSerializationTime" units="ms"
     expires_after="2019-01-24">
+  <obsolete>
+    Removed 11/2018 as we no longer record this metric.
+  </obsolete>
   <owner>chengx@chromium.org</owner>
   <owner>wittman@chromium.org</owner>
   <summary>Amount of time taken to serialize a call stack profile.</summary>