From 7ed4f0ca2746d3bd8ecc79849bfcc4337c706faf Mon Sep 17 00:00:00 2001
From: Charles Kerr <charles@charleskerr.com>
Date: Mon, 24 Mar 2025 04:09:14 -0500
Subject: [PATCH] perf: use `absl::flat_hash_map` instead of
 `std::unordered_map` (#46202)

* perf: make ElectronUsbDelegate::controller_map_ an absl::flat_hash_map

* perf: make ElectronSerialDelegate::controller_map_ an absl::flat_hash_map

* perf: make ElectronHidDelegate::controller_map_ an absl::flat_hash_map

* perf: make FrameTreeNodeIdMap an absl::flat_hash_map

* perf: make AutofillDriverFactory::driver_map_ an absl::flat_hash_map

* perf: make asar::Archive::external_files_ an absl::flat_hash_map

* perf: make VersionIdMap an absl::flat_hash_map

* perf: make ObjectCache::proxy_map_ an absl::flat_hash_map

* docs: add TODO to investigate absl map in KeyWeakMap
---
 shell/browser/api/electron_api_service_worker_main.cc | 9 ++++-----
 shell/browser/api/electron_api_web_frame_main.cc      | 4 ++--
 shell/browser/electron_autofill_driver_factory.h      | 5 +++--
 shell/browser/hid/electron_hid_delegate.h             | 6 +++---
 shell/browser/serial/electron_serial_delegate.h       | 6 +++---
 shell/browser/usb/electron_usb_delegate.h             | 6 +++---
 shell/common/asar/archive.h                           | 6 +++---
 shell/common/key_weak_map.h                           | 1 +
 shell/renderer/api/context_bridge/object_cache.h      | 5 ++---
 9 files changed, 24 insertions(+), 24 deletions(-)

diff --git a/shell/browser/api/electron_api_service_worker_main.cc b/shell/browser/api/electron_api_service_worker_main.cc
index 585822147df2..25ccf1f39187 100644
--- a/shell/browser/api/electron_api_service_worker_main.cc
+++ b/shell/browser/api/electron_api_service_worker_main.cc
@@ -5,7 +5,6 @@
 #include "shell/browser/api/electron_api_service_worker_main.h"
 
 #include <string>
-#include <unordered_map>
 #include <utility>
 
 #include "base/logging.h"
@@ -28,6 +27,7 @@
 #include "shell/common/gin_helper/promise.h"
 #include "shell/common/node_includes.h"
 #include "shell/common/v8_util.h"
+#include "third_party/abseil-cpp/absl/container/flat_hash_map.h"
 
 namespace {
 
@@ -58,10 +58,9 @@ std::optional<content::ServiceWorkerVersionBaseInfo> GetLiveVersionInfo(
 namespace electron::api {
 
 // ServiceWorkerKey -> ServiceWorkerMain*
-typedef std::unordered_map<ServiceWorkerKey,
-                           ServiceWorkerMain*,
-                           ServiceWorkerKey::Hasher>
-    VersionIdMap;
+using VersionIdMap = absl::flat_hash_map<ServiceWorkerKey,
+                                         ServiceWorkerMain*,
+                                         ServiceWorkerKey::Hasher>;
 
 VersionIdMap& GetVersionIdMap() {
   static base::NoDestructor<VersionIdMap> instance;
diff --git a/shell/browser/api/electron_api_web_frame_main.cc b/shell/browser/api/electron_api_web_frame_main.cc
index c018b7138616..d554cf1a3391 100644
--- a/shell/browser/api/electron_api_web_frame_main.cc
+++ b/shell/browser/api/electron_api_web_frame_main.cc
@@ -5,7 +5,6 @@
 #include "shell/browser/api/electron_api_web_frame_main.h"
 
 #include <string>
-#include <unordered_map>
 #include <utility>
 #include <vector>
 
@@ -36,6 +35,7 @@
 #include "shell/common/gin_helper/promise.h"
 #include "shell/common/node_includes.h"
 #include "shell/common/v8_util.h"
+#include "third_party/abseil-cpp/absl/container/flat_hash_map.h"
 
 namespace {
 
@@ -99,7 +99,7 @@ namespace electron::api {
 // Using FrameTreeNode allows us to track frame across navigations. This
 // is most similar to how <iframe> works.
 using FrameTreeNodeIdMap =
-    std::unordered_map<content::FrameTreeNodeId, WebFrameMain*>;
+    absl::flat_hash_map<content::FrameTreeNodeId, WebFrameMain*>;
 
 // Token -> WebFrameMain*
 // Maps exact RFH to a WebFrameMain instance.
diff --git a/shell/browser/electron_autofill_driver_factory.h b/shell/browser/electron_autofill_driver_factory.h
index 84734411e565..385a2a985a62 100644
--- a/shell/browser/electron_autofill_driver_factory.h
+++ b/shell/browser/electron_autofill_driver_factory.h
@@ -6,12 +6,12 @@
 #define ELECTRON_SHELL_BROWSER_ELECTRON_AUTOFILL_DRIVER_FACTORY_H_
 
 #include <memory>
-#include <unordered_map>
 
 #include "base/functional/callback_forward.h"
 #include "content/public/browser/web_contents_observer.h"
 #include "content/public/browser/web_contents_user_data.h"
 #include "shell/common/api/api.mojom.h"
+#include "third_party/abseil-cpp/absl/container/flat_hash_map.h"
 
 namespace electron {
 
@@ -49,7 +49,8 @@ class AutofillDriverFactory
   explicit AutofillDriverFactory(content::WebContents* web_contents);
   friend class content::WebContentsUserData<AutofillDriverFactory>;
 
-  std::unordered_map<content::RenderFrameHost*, std::unique_ptr<AutofillDriver>>
+  absl::flat_hash_map<content::RenderFrameHost*,
+                      std::unique_ptr<AutofillDriver>>
       driver_map_;
 };
 
diff --git a/shell/browser/hid/electron_hid_delegate.h b/shell/browser/hid/electron_hid_delegate.h
index b1c1f877899a..04b1a60ea8cb 100644
--- a/shell/browser/hid/electron_hid_delegate.h
+++ b/shell/browser/hid/electron_hid_delegate.h
@@ -7,13 +7,13 @@
 
 #include <memory>
 #include <string>
-#include <unordered_map>
 #include <vector>
 
 #include "base/containers/flat_map.h"
 #include "content/public/browser/hid_chooser.h"
 #include "content/public/browser/hid_delegate.h"
 #include "services/device/public/mojom/hid.mojom-forward.h"
+#include "third_party/abseil-cpp/absl/container/flat_hash_map.h"
 #include "third_party/blink/public/mojom/hid/hid.mojom-forward.h"
 #include "url/origin.h"
 
@@ -87,8 +87,8 @@ class ElectronHidDelegate : public content::HidDelegate {
       std::vector<blink::mojom::HidDeviceFilterPtr> exclusion_filters,
       content::HidChooser::Callback callback);
 
-  std::unordered_map<content::RenderFrameHost*,
-                     std::unique_ptr<HidChooserController>>
+  absl::flat_hash_map<content::RenderFrameHost*,
+                      std::unique_ptr<HidChooserController>>
       controller_map_;
 
   base::WeakPtrFactory<ElectronHidDelegate> weak_factory_{this};
diff --git a/shell/browser/serial/electron_serial_delegate.h b/shell/browser/serial/electron_serial_delegate.h
index ea95e803c4e7..62041f66ba7f 100644
--- a/shell/browser/serial/electron_serial_delegate.h
+++ b/shell/browser/serial/electron_serial_delegate.h
@@ -6,7 +6,6 @@
 #define ELECTRON_SHELL_BROWSER_SERIAL_ELECTRON_SERIAL_DELEGATE_H_
 
 #include <memory>
-#include <unordered_map>
 #include <vector>
 
 #include "base/memory/weak_ptr.h"
@@ -15,6 +14,7 @@
 #include "content/public/browser/serial_delegate.h"
 #include "shell/browser/serial/serial_chooser_context.h"
 #include "shell/browser/serial/serial_chooser_controller.h"
+#include "third_party/abseil-cpp/absl/container/flat_hash_map.h"
 
 namespace electron {
 
@@ -77,8 +77,8 @@ class ElectronSerialDelegate : public content::SerialDelegate,
       port_observation_{this};
   base::ObserverList<content::SerialDelegate::Observer> observer_list_;
 
-  std::unordered_map<content::RenderFrameHost*,
-                     std::unique_ptr<SerialChooserController>>
+  absl::flat_hash_map<content::RenderFrameHost*,
+                      std::unique_ptr<SerialChooserController>>
       controller_map_;
 
   base::WeakPtrFactory<ElectronSerialDelegate> weak_factory_{this};
diff --git a/shell/browser/usb/electron_usb_delegate.h b/shell/browser/usb/electron_usb_delegate.h
index 673fc346776a..03a1e7a550a8 100644
--- a/shell/browser/usb/electron_usb_delegate.h
+++ b/shell/browser/usb/electron_usb_delegate.h
@@ -7,7 +7,6 @@
 
 #include <memory>
 #include <string>
-#include <unordered_map>
 #include <vector>
 
 #include "base/containers/span.h"
@@ -17,6 +16,7 @@
 #include "services/device/public/mojom/usb_device.mojom-forward.h"
 #include "services/device/public/mojom/usb_enumeration_options.mojom-forward.h"
 #include "services/device/public/mojom/usb_manager.mojom-forward.h"
+#include "third_party/abseil-cpp/absl/container/flat_hash_map.h"
 #include "third_party/blink/public/mojom/usb/web_usb_service.mojom.h"
 #include "url/origin.h"
 
@@ -111,8 +111,8 @@ class ElectronUsbDelegate : public content::UsbDelegate {
   base::flat_map<content::BrowserContext*, std::unique_ptr<ContextObservation>>
       observations_;
 
-  std::unordered_map<content::RenderFrameHost*,
-                     std::unique_ptr<UsbChooserController>>
+  absl::flat_hash_map<content::RenderFrameHost*,
+                      std::unique_ptr<UsbChooserController>>
       controller_map_;
 
   base::WeakPtrFactory<ElectronUsbDelegate> weak_factory_{this};
diff --git a/shell/common/asar/archive.h b/shell/common/asar/archive.h
index 16898e1f731b..5b38b0114bd7 100644
--- a/shell/common/asar/archive.h
+++ b/shell/common/asar/archive.h
@@ -8,7 +8,6 @@
 #include <memory>
 #include <optional>
 #include <string>
-#include <unordered_map>
 #include <vector>
 
 #include <uv.h>
@@ -17,6 +16,7 @@
 #include "base/files/file_path.h"
 #include "base/synchronization/lock.h"
 #include "base/values.h"
+#include "third_party/abseil-cpp/absl/container/flat_hash_map.h"
 
 namespace asar {
 
@@ -110,8 +110,8 @@ class Archive {
 
   // Cached external temporary files.
   base::Lock external_files_lock_;
-  std::unordered_map<base::FilePath::StringType,
-                     std::unique_ptr<ScopedTemporaryFile>>
+  absl::flat_hash_map<base::FilePath::StringType,
+                      std::unique_ptr<ScopedTemporaryFile>>
       external_files_;
 };
 
diff --git a/shell/common/key_weak_map.h b/shell/common/key_weak_map.h
index b064ed627d1f..2df52e719387 100644
--- a/shell/common/key_weak_map.h
+++ b/shell/common/key_weak_map.h
@@ -69,6 +69,7 @@ class KeyWeakMap {
   }
 
   // Map of stored objects.
+  // TODO(ckerr): can absl::flat_hash_map be used safely here?
   std::unordered_map<K, Mapped> map_;
 };
 
diff --git a/shell/renderer/api/context_bridge/object_cache.h b/shell/renderer/api/context_bridge/object_cache.h
index 340d1bebc28a..297ae81415ce 100644
--- a/shell/renderer/api/context_bridge/object_cache.h
+++ b/shell/renderer/api/context_bridge/object_cache.h
@@ -5,8 +5,7 @@
 #ifndef ELECTRON_SHELL_RENDERER_API_CONTEXT_BRIDGE_OBJECT_CACHE_H_
 #define ELECTRON_SHELL_RENDERER_API_CONTEXT_BRIDGE_OBJECT_CACHE_H_
 
-#include <unordered_map>
-
+#include "third_party/abseil-cpp/absl/container/flat_hash_map.h"
 #include "v8/include/v8-local-handle.h"
 #include "v8/include/v8-object.h"
 
@@ -35,7 +34,7 @@ class ObjectCache final {
   };
 
   // from_object ==> proxy_value
-  std::unordered_map<v8::Local<v8::Object>, v8::Local<v8::Value>, Hash>
+  absl::flat_hash_map<v8::Local<v8::Object>, v8::Local<v8::Value>, Hash>
       proxy_map_;
 };