[heap profile] Report allocations count in UMA heap profiles.

BUG=878604

Change-Id: I0321b48834ccf85db9e72cb5942d2c53f8af3aac
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1628109Reviewed-by: Mike Wittman <wittman@chromium.org>
Commit-Queue: Alexei Filippov <alph@chromium.org>
Cr-Commit-Position: refs/heads/master@{#663172}

chrome/common/heap_profiler_controller.cc

@@ -87,7 +87,11 @@ void HeapProfilerController::RetrieveAndSendSnapshot() {
           module_cache.GetModuleForAddress(address);
       frames.emplace_back(address, module);
     }
-    profile_builder.OnSampleCompleted(std::move(frames), sample.total);
+    size_t count = std::max<size_t>(
+        static_cast<size_t>(
+            std::llround(static_cast<double>(sample.total) / sample.size)),
+        1);
+    profile_builder.OnSampleCompleted(std::move(frames), sample.total, count);
   }
 
   profile_builder.OnProfileCompleted(base::TimeDelta(), base::TimeDelta());

components/metrics/call_stack_profile_builder.cc

@@ -139,11 +139,12 @@ void CallStackProfileBuilder::RecordMetadata() {
 
 void CallStackProfileBuilder::OnSampleCompleted(
     std::vector<base::Frame> frames) {
-  OnSampleCompleted(std::move(frames), 1);
+  OnSampleCompleted(std::move(frames), 1, 1);
 }
 
 void CallStackProfileBuilder::OnSampleCompleted(std::vector<base::Frame> frames,
-                                                size_t weight) {
+                                                size_t weight,
+                                                size_t count) {
   // Write CallStackProfile::Stack protobuf message.
   CallStackProfile::Stack stack;
 
@@ -193,6 +194,8 @@ void CallStackProfileBuilder::OnSampleCompleted(std::vector<base::Frame> frames,
   stack_sample_proto->set_stack_index(stack_loc->second);
   if (weight != 1)
     stack_sample_proto->set_weight(weight);
+  if (count != 1)
+    stack_sample_proto->set_count(count);
   if (is_continued_work_)
     stack_sample_proto->set_continued_work(is_continued_work_);
 

components/metrics/call_stack_profile_builder.h

@@ -62,8 +62,10 @@ class CallStackProfileBuilder : public base::ProfileBuilder {
 
   ~CallStackProfileBuilder() override;
 
-  // The weight is used by the heap profiler only.
-  void OnSampleCompleted(std::vector<base::Frame> frames, size_t weight);
+  // Both weight and count are used by the heap profiler only.
+  void OnSampleCompleted(std::vector<base::Frame> frames,
+                         size_t weight,
+                         size_t count);
 
   // base::ProfileBuilder:
   base::ModuleCache* GetModuleCache() override;

components/metrics/call_stack_profile_builder_unittest.cc

@@ -176,7 +176,7 @@ TEST(CallStackProfileBuilderTest, ProfilingCompleted) {
   EXPECT_EQ(100, profile.sampling_period_ms());
 }
 
-TEST(CallStackProfileBuilderTest, CustomWeights) {
+TEST(CallStackProfileBuilderTest, CustomWeightsAndCounts) {
   auto profile_builder =
       std::make_unique<TestingCallStackProfileBuilder>(kProfileParams);
 
@@ -184,8 +184,8 @@ TEST(CallStackProfileBuilderTest, CustomWeights) {
   base::Frame frame1 = {0x10, &module1};
   std::vector<base::Frame> frames = {frame1};
 
-  profile_builder->OnSampleCompleted(frames, 42);
-  profile_builder->OnSampleCompleted(frames, 1);
+  profile_builder->OnSampleCompleted(frames, 42, 3);
+  profile_builder->OnSampleCompleted(frames, 1, 1);
   profile_builder->OnSampleCompleted(frames);
   profile_builder->OnProfileCompleted(base::TimeDelta(), base::TimeDelta());
 
@@ -195,9 +195,13 @@ TEST(CallStackProfileBuilderTest, CustomWeights) {
   const CallStackProfile& profile = proto.call_stack_profile();
   ASSERT_EQ(3, profile.stack_sample_size());
   EXPECT_TRUE(profile.stack_sample(0).has_weight());
+  EXPECT_TRUE(profile.stack_sample(0).has_count());
   EXPECT_EQ(42, profile.stack_sample(0).weight());
+  EXPECT_EQ(3, profile.stack_sample(0).count());
   EXPECT_FALSE(profile.stack_sample(1).has_weight());
+  EXPECT_FALSE(profile.stack_sample(1).has_count());
   EXPECT_FALSE(profile.stack_sample(2).has_weight());
+  EXPECT_FALSE(profile.stack_sample(2).has_count());
 }
 
 TEST(CallStackProfileBuilderTest, StacksDeduped) {