diff --git chrome/browser/BUILD.gn chrome/browser/BUILD.gn
index 44d3b5e543101..09b095cffd89e 100644
--- chrome/browser/BUILD.gn
+++ chrome/browser/BUILD.gn
@@ -11,6 +11,7 @@ import("//build/config/compiler/pgo/pgo.gni")
 import("//build/config/features.gni")
 import("//build/config/python.gni")
 import("//build/config/ui.gni")
+import("//cef/libcef/features/features.gni")
 import("//chrome/browser/buildflags.gni")
 import("//chrome/browser/downgrade/buildflags.gni")
 import("//chrome/common/features.gni")
@@ -110,7 +111,8 @@ buildflag_header("buildflags") {
 
   # Android and ChromeOS don't support multiple browser processes, so they don't
   # employ ProcessSingleton.
-  if (is_android || is_chromeos) {
+  # Also disable for CEF (see issue #3609).
+  if (is_android || is_chromeos || enable_cef) {
     flags += [ "ENABLE_PROCESS_SINGLETON=0" ]
   } else {
     flags += [ "ENABLE_PROCESS_SINGLETON=1" ]
@@ -2075,6 +2077,7 @@ static_library("browser") {
     "//build/config/chromebox_for_meetings:buildflags",
     "//build/config/compiler:compiler_buildflags",
     "//cc",
+    "//cef/libcef/features",
     "//chrome:extra_resources",
     "//chrome:resources",
     "//chrome:strings",
@@ -2731,6 +2734,10 @@ static_library("browser") {
     ]
   }
 
+  if (enable_cef) {
+    configs += [ "//cef/libcef/features:config" ]
+  }
+
   if (is_android) {
     sources += [
       "accessibility/accessibility_prefs/android/accessibility_prefs_controller.cc",
diff --git chrome/browser/browser_process_platform_part_win.cc chrome/browser/browser_process_platform_part_win.cc
index 66fa1aa8b10b3..9b506f6d153ae 100644
--- chrome/browser/browser_process_platform_part_win.cc
+++ chrome/browser/browser_process_platform_part_win.cc
@@ -9,6 +9,7 @@
 BrowserProcessPlatformPart::BrowserProcessPlatformPart() = default;
 BrowserProcessPlatformPart::~BrowserProcessPlatformPart() = default;
 
+#if BUILDFLAG(ENABLE_PROCESS_SINGLETON)
 void BrowserProcessPlatformPart::OnBrowserLaunch() {
   if constexpr (kShouldRecordActiveUse) {
     if (!did_run_updater_) {
@@ -16,3 +17,4 @@ void BrowserProcessPlatformPart::OnBrowserLaunch() {
     }
   }
 }
+#endif  // BUILDFLAG(ENABLE_PROCESS_SINGLETON)
diff --git chrome/browser/browser_process_platform_part_win.h chrome/browser/browser_process_platform_part_win.h
index fc4b9808f3f6e..92cef9459811f 100644
--- chrome/browser/browser_process_platform_part_win.h
+++ chrome/browser/browser_process_platform_part_win.h
@@ -18,10 +18,12 @@ class BrowserProcessPlatformPart : public BrowserProcessPlatformPartBase {
   ~BrowserProcessPlatformPart() override;
 
   // BrowserProcessPlatformPartBase:
+#if BUILDFLAG(ENABLE_PROCESS_SINGLETON)
   void OnBrowserLaunch() override;
 
  private:
   absl::optional<DidRunUpdater> did_run_updater_;
+#endif  // BUILDFLAG(ENABLE_PROCESS_SINGLETON)
 };
 
 #endif  // CHROME_BROWSER_BROWSER_PROCESS_PLATFORM_PART_WIN_H_