From 5190ee9f96419e132bc71215495730791b7aae4a Mon Sep 17 00:00:00 2001
From: Drew Thomas <async@google.com>
Date: Wed, 21 Aug 2024 09:32:22 -0700
Subject: [PATCH] Add `performance.memory.jsHeapSizeLimit` support (#3928)

This value, in combination with the existing `totalJSHeapSize` and
`usedJSHeapSize` values, can help describe memory usage of a webpage.

See the MDN reference:

https://developer.mozilla.org/en-US/docs/Web/API/Performance/memory#value

b/355487905
---
 cobalt/dom/memory_info.cc         | 14 ++++++++++++++
 cobalt/dom/memory_info.h          |  2 ++
 cobalt/dom/memory_info.idl        |  1 +
 cobalt/script/javascript_engine.h |  1 +
 cobalt/script/v8c/v8c_engine.cc   |  3 ++-
 5 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/cobalt/dom/memory_info.cc b/cobalt/dom/memory_info.cc
index d6875450f7bd0..1c6619e6cc760 100644
--- a/cobalt/dom/memory_info.cc
+++ b/cobalt/dom/memory_info.cc
@@ -61,6 +61,20 @@ uint32 MemoryInfo::used_js_heap_size(
           .used_heap_size);
 }
 
+uint32 MemoryInfo::js_heap_size_limit(
+    script::EnvironmentSettings* environment_settings) const {
+  if (!environment_settings) {
+    return 0u;
+  }
+  return static_cast<uint32>(
+      base::polymorphic_downcast<web::EnvironmentSettings*>(
+          environment_settings)
+          ->context()
+          ->javascript_engine()
+          ->GetHeapStatistics()
+          .heap_size_limit);
+}
+
 uint32 MemoryInfo::media_source_size_limit(
     script::EnvironmentSettings* environment_settings) const {
   auto memory_info = GetDecoderBufferMemoryInfo(environment_settings);
diff --git a/cobalt/dom/memory_info.h b/cobalt/dom/memory_info.h
index a6e4dcfd50b2a..5d1dd57d10ffd 100644
--- a/cobalt/dom/memory_info.h
+++ b/cobalt/dom/memory_info.h
@@ -33,6 +33,8 @@ class MemoryInfo : public script::Wrappable {
       script::EnvironmentSettings* environment_settings) const;
   uint32 used_js_heap_size(
       script::EnvironmentSettings* environment_settings) const;
+  uint32 js_heap_size_limit(
+      script::EnvironmentSettings* environment_settings) const;
   uint32 media_source_size_limit(
       script::EnvironmentSettings* environment_settings) const;
   uint32 total_media_source_size(
diff --git a/cobalt/dom/memory_info.idl b/cobalt/dom/memory_info.idl
index 4308390a6b80b..16257fae9076e 100644
--- a/cobalt/dom/memory_info.idl
+++ b/cobalt/dom/memory_info.idl
@@ -20,6 +20,7 @@
 ] interface MemoryInfo {
   [CallWith=EnvironmentSettings] readonly attribute unsigned long totalJSHeapSize;
   [CallWith=EnvironmentSettings] readonly attribute unsigned long usedJSHeapSize;
+  [CallWith=EnvironmentSettings] readonly attribute unsigned long jsHeapSizeLimit;
 
   [CallWith=EnvironmentSettings] readonly attribute unsigned long mediaSourceSizeLimit;
   [CallWith=EnvironmentSettings] readonly attribute unsigned long totalMediaSourceSize;
diff --git a/cobalt/script/javascript_engine.h b/cobalt/script/javascript_engine.h
index 55124a79294c6..a7807a7e499b4 100644
--- a/cobalt/script/javascript_engine.h
+++ b/cobalt/script/javascript_engine.h
@@ -31,6 +31,7 @@ class GlobalEnvironment;
 struct HeapStatistics {
   size_t total_heap_size;
   size_t used_heap_size;
+  size_t heap_size_limit;
 };
 
 class JavaScriptEngine {
diff --git a/cobalt/script/v8c/v8c_engine.cc b/cobalt/script/v8c/v8c_engine.cc
index 2caa5fa61be21..89e7a135167f7 100644
--- a/cobalt/script/v8c/v8c_engine.cc
+++ b/cobalt/script/v8c/v8c_engine.cc
@@ -206,7 +206,8 @@ HeapStatistics V8cEngine::GetHeapStatistics() {
   v8::HeapStatistics v8_heap_statistics;
   isolate_->GetHeapStatistics(&v8_heap_statistics);
   return {v8_heap_statistics.total_heap_size(),
-          v8_heap_statistics.used_heap_size()};
+          v8_heap_statistics.used_heap_size(),
+          v8_heap_statistics.heap_size_limit()};
 }
 
 void V8cEngine::UpdateDateTimeConfiguration() {