Partially deduplicate PostMessage.Incoming.* UKM event recording

To decrease UKM volume, this maintains a list of the 20 most recently
recorded (source, target) UKM source ID pairs, such that duplicates can
be skipped.

Bug: 1112491
Change-Id: I4b6bfe26f55102078305bc7a5c3bc1a774ca62d2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2622277Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Aaron Colwell <acolwell@chromium.org>
Commit-Queue: Lily Chen <chlily@chromium.org>
Cr-Commit-Position: refs/heads/master@{#842718}

content/browser/renderer_host/render_frame_proxy_host.cc

@@ -9,8 +9,10 @@
 #include <vector>
 
 #include "base/callback.h"
+#include "base/containers/circular_deque.h"
 #include "base/hash/hash.h"
 #include "base/lazy_instance.h"
+#include "base/no_destructor.h"
 #include "content/browser/bad_message.h"
 #include "content/browser/blob_storage/chrome_blob_storage_context.h"
 #include "content/browser/child_process_security_policy_impl.h"
@@ -71,6 +73,35 @@ using TokenFrameMap = std::unordered_map<base::UnguessableToken,
 base::LazyInstance<TokenFrameMap>::Leaky g_token_frame_proxy_map =
     LAZY_INSTANCE_INITIALIZER;
 
+// Maintains a list of the most recently recorded (source, target) pairs for the
+// PostMessage.Incoming.Page UKM event, in order to partially deduplicate
+// logged events. Its size is limited to 20. See RouteMessageEvent() where
+// this UKM is logged.
+// TODO(crbug.com/1112491): Remove when no longer needed.
+bool ShouldRecordPostMessageIncomingPageUkmEvent(
+    ukm::SourceId source_page_ukm_source_id,
+    ukm::SourceId target_page_ukm_source_id) {
+  constexpr size_t kMaxPostMessageUkmAlreadyRecordedPairsSize = 20;
+  static base::NoDestructor<
+      base::circular_deque<std::pair<ukm::SourceId, ukm::SourceId>>>
+      s_post_message_ukm_already_recorded_pairs;
+
+  DCHECK_LE(s_post_message_ukm_already_recorded_pairs->size(),
+            kMaxPostMessageUkmAlreadyRecordedPairsSize);
+  std::pair<ukm::SourceId, ukm::SourceId> new_pair =
+      std::make_pair(source_page_ukm_source_id, target_page_ukm_source_id);
+
+  if (base::Contains(*s_post_message_ukm_already_recorded_pairs, new_pair))
+    return false;
+
+  if (s_post_message_ukm_already_recorded_pairs->size() ==
+      kMaxPostMessageUkmAlreadyRecordedPairsSize) {
+    s_post_message_ukm_already_recorded_pairs->pop_back();
+  }
+  s_post_message_ukm_already_recorded_pairs->push_front(new_pair);
+  return true;
+}
+
 }  // namespace
 
 // static
@@ -595,11 +626,15 @@ void RenderFrameProxyHost::RouteMessageEvent(
   }
 
   // Record UKM metrics for the postMessage event.
-  ukm::builders::PostMessage_Incoming_Page ukm_builder(
-      target_rfh->GetPageUkmSourceId());
-  if (source_page_ukm_source_id != ukm::kInvalidSourceId)
-    ukm_builder.SetSourcePageSourceId(source_page_ukm_source_id);
-  ukm_builder.Record(ukm::UkmRecorder::Get());
+  ukm::SourceId target_page_ukm_source_id = target_rfh->GetPageUkmSourceId();
+  if (ShouldRecordPostMessageIncomingPageUkmEvent(source_page_ukm_source_id,
+                                                  target_page_ukm_source_id)) {
+    ukm::builders::PostMessage_Incoming_Page ukm_builder(
+        target_page_ukm_source_id);
+    if (source_page_ukm_source_id != ukm::kInvalidSourceId)
+      ukm_builder.SetSourcePageSourceId(source_page_ukm_source_id);
+    ukm_builder.Record(ukm::UkmRecorder::Get());
+  }
 
   target_rfh->PostMessageEvent(translated_source_token, source_origin,
                                target_origin, std::move(message));

third_party/blink/renderer/core/frame/local_dom_window.cc

@@ -137,6 +137,31 @@
 
 namespace blink {
 
+namespace {
+
+constexpr size_t kMaxPostMessageUkmRecordedSourceIdsSize = 20;
+
+bool ShouldRecordPostMessageIncomingFrameUkmEvent(
+    ukm::SourceId source_frame_ukm_source_id,
+    Deque<ukm::SourceId>& already_recorded_source_frame_ids) {
+  DCHECK_LE(already_recorded_source_frame_ids.size(),
+            kMaxPostMessageUkmRecordedSourceIdsSize);
+
+  if (base::Contains(already_recorded_source_frame_ids,
+                     source_frame_ukm_source_id)) {
+    return false;
+  }
+
+  if (already_recorded_source_frame_ids.size() ==
+      kMaxPostMessageUkmRecordedSourceIdsSize) {
+    already_recorded_source_frame_ids.pop_back();
+  }
+  already_recorded_source_frame_ids.push_front(source_frame_ukm_source_id);
+  return true;
+}
+
+}  // namespace
+
 LocalDOMWindow::LocalDOMWindow(LocalFrame& frame, WindowAgent* agent)
     : DOMWindow(frame),
       ExecutionContext(V8PerIsolateData::MainThreadIsolate(), agent),
@@ -945,9 +970,13 @@ void LocalDOMWindow::SchedulePostMessage(
     scoped_refptr<const SecurityOrigin> target,
     LocalDOMWindow* source) {
   // Record UKM metrics for postMessage event.
-  ukm::builders::PostMessage_Incoming_Frame(UkmSourceID())
-      .SetSourceFrameSourceId(source->UkmSourceID())
-      .Record(UkmRecorder());
+  ukm::SourceId source_frame_ukm_source_id = source->UkmSourceID();
+  if (ShouldRecordPostMessageIncomingFrameUkmEvent(
+          source_frame_ukm_source_id, post_message_ukm_recorded_source_ids_)) {
+    ukm::builders::PostMessage_Incoming_Frame(UkmSourceID())
+        .SetSourceFrameSourceId(source_frame_ukm_source_id)
+        .Record(UkmRecorder());
+  }
 
   // Allowing unbounded amounts of messages to build up for a suspended context
   // is problematic; consider imposing a limit or other restriction if this

third_party/blink/renderer/core/frame/local_dom_window.h

@@ -531,6 +531,13 @@ class CORE_EXPORT LocalDOMWindow final : public DOMWindow,
   // this document, to avoid reporting duplicates. The value stored comes
   // from |DocumentPolicyViolationReport::MatchId()|.
   mutable HashSet<unsigned> document_policy_violation_reports_sent_;
+
+  // A list of the most recently recorded source frame UKM source IDs for the
+  // PostMessage.Incoming.Frame UKM event, in order to partially deduplicate
+  // logged events. Its size is limited to 20. See SchedulePostMessage() where
+  // this UKM is logged.
+  // TODO(crbug.com/1112491): Remove when no longer needed.
+  Deque<ukm::SourceId> post_message_ukm_recorded_source_ids_;
 };
 
 template <>