Store serialized profiles in ChildCallStackProfileCollector to save memory

Bug: 888716, 851163
Change-Id: I0fce8657b8ab41c0ac57bff548a029bab302c8b3
Reviewed-on: https://chromium-review.googlesource.com/c/1256106Reviewed-by: Ilya Sherman <isherman@chromium.org>
Commit-Queue: Xi Cheng <chengx@chromium.org>
Cr-Commit-Position: refs/heads/master@{#595901}

components/metrics/child_call_stack_profile_collector.cc

@@ -11,6 +11,7 @@
 #include "base/synchronization/lock.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "base/time/time.h"
+#include "third_party/metrics_proto/sampled_profile.pb.h"
 
 namespace metrics {
 
@@ -20,7 +21,7 @@ ChildCallStackProfileCollector::ProfileState::ProfileState(ProfileState&&) =
 
 ChildCallStackProfileCollector::ProfileState::ProfileState(
     base::TimeTicks start_timestamp,
-    SampledProfile profile)
+    std::string profile)
     : start_timestamp(start_timestamp), profile(std::move(profile)) {}
 
 ChildCallStackProfileCollector::ProfileState::~ProfileState() = default;
@@ -48,7 +49,7 @@ void ChildCallStackProfileCollector::SetParentProfileCollector(
   if (parent_collector_) {
     for (ProfileState& state : profiles_) {
       mojom::SampledProfilePtr mojo_profile = mojom::SampledProfile::New();
-      state.profile.SerializeToString(&mojo_profile->contents);
+      mojo_profile->contents = std::move(state.profile);
       parent_collector_->Collect(state.start_timestamp,
                                  std::move(mojo_profile));
     }
@@ -77,8 +78,13 @@ void ChildCallStackProfileCollector::Collect(base::TimeTicks start_timestamp,
     mojom::SampledProfilePtr mojo_profile = mojom::SampledProfile::New();
     profile.SerializeToString(&mojo_profile->contents);
     parent_collector_->Collect(start_timestamp, std::move(mojo_profile));
-  } else if (retain_profiles_) {
-    profiles_.push_back(ProfileState(start_timestamp, std::move(profile)));
+    return;
+  }
+
+  if (retain_profiles_) {
+    std::string serialized_profile;
+    profile.SerializeToString(&serialized_profile);
+    profiles_.emplace_back(start_timestamp, std::move(serialized_profile));
   }
 }
 

components/metrics/child_call_stack_profile_collector.h

@@ -5,6 +5,7 @@
 #ifndef COMPONENTS_METRICS_CHILD_CALL_STACK_PROFILE_COLLECTOR_H_
 #define COMPONENTS_METRICS_CHILD_CALL_STACK_PROFILE_COLLECTOR_H_
 
+#include <string>
 #include <vector>
 
 #include "base/macros.h"
@@ -12,7 +13,6 @@
 #include "base/single_thread_task_runner.h"
 #include "base/synchronization/lock.h"
 #include "components/metrics/public/interfaces/call_stack_profile_collector.mojom.h"
-#include "third_party/metrics_proto/sampled_profile.pb.h"
 
 namespace service_manager {
 class InterfaceProvider;
@@ -20,6 +20,8 @@ class InterfaceProvider;
 
 namespace metrics {
 
+class SampledProfile;
+
 // ChildCallStackProfileCollector collects stacks at startup, caching them
 // internally until a CallStackProfileCollector interface is available. If a
 // CallStackProfileCollector is provided via the InterfaceProvider supplied to
@@ -63,21 +65,21 @@ class ChildCallStackProfileCollector {
  private:
   friend class ChildCallStackProfileCollectorTest;
 
-  // Bundles together a collected profile and the collection state for
-  // storage, pending availability of the parent mojo interface. |profile|
+  // Bundles together a collected serialized profile and the collection state
+  // for storage, pending availability of the parent mojo interface. |profile|
   // is not const& because it must be passed with std::move.
   struct ProfileState {
     ProfileState();
     ProfileState(ProfileState&&);
-    ProfileState(base::TimeTicks start_timestamp, SampledProfile profile);
+    ProfileState(base::TimeTicks start_timestamp, std::string profile);
     ~ProfileState();
 
     ProfileState& operator=(ProfileState&&);
 
     base::TimeTicks start_timestamp;
 
-    // The sampled profile.
-    SampledProfile profile;
+    // The serialized sampled profile.
+    std::string profile;
 
    private:
     DISALLOW_COPY_AND_ASSIGN(ProfileState);

components/metrics/child_call_stack_profile_collector_unittest.cc

@@ -13,6 +13,7 @@
 #include "base/run_loop.h"
 #include "mojo/public/cpp/bindings/binding.h"
 #include "testing/gtest/include/gtest/gtest.h"
+#include "third_party/metrics_proto/sampled_profile.pb.h"
 
 namespace metrics {