diff --git a/shell/browser/electron_browser_client.cc b/shell/browser/electron_browser_client.cc
index 760cb8b1d2..5426960fb4 100644
--- a/shell/browser/electron_browser_client.cc
+++ b/shell/browser/electron_browser_client.cc
@@ -61,6 +61,7 @@
 #include "mojo/public/cpp/bindings/self_owned_associated_receiver.h"
 #include "net/ssl/ssl_cert_request_info.h"
 #include "net/ssl/ssl_private_key.h"
+#include "pdf/pdf_features.h"
 #include "printing/buildflags/buildflags.h"
 #include "services/device/public/cpp/geolocation/geolocation_system_permission_manager.h"
 #include "services/device/public/cpp/geolocation/location_provider.h"
@@ -1587,6 +1588,46 @@ bool ElectronBrowserClient::ShouldEnableStrictSiteIsolation() {
   return true;
 }
 
+bool ElectronBrowserClient::ShouldEnableSubframeZoom() {
+#if BUILDFLAG(ENABLE_PDF_VIEWER)
+  return chrome_pdf::features::IsOopifPdfEnabled();
+#else
+  return false;
+#endif
+}
+
+#if BUILDFLAG(ENABLE_PDF_VIEWER)
+std::optional<network::CrossOriginEmbedderPolicy>
+ElectronBrowserClient::MaybeOverrideLocalURLCrossOriginEmbedderPolicy(
+    content::NavigationHandle* navigation_handle) {
+  if (!chrome_pdf::features::IsOopifPdfEnabled() ||
+      !navigation_handle->IsPdf()) {
+    return std::nullopt;
+  }
+
+  content::RenderFrameHost* pdf_extension = navigation_handle->GetParentFrame();
+  if (!pdf_extension) {
+    return std::nullopt;
+  }
+
+  content::RenderFrameHost* pdf_embedder = pdf_extension->GetParent();
+  CHECK(pdf_embedder);
+  return pdf_embedder->GetCrossOriginEmbedderPolicy();
+}
+#endif  // BUILDFLAG(ENABLE_PDF_VIEWER)
+
+bool ElectronBrowserClient::DoesSiteRequireDedicatedProcess(
+    content::BrowserContext* browser_context,
+    const GURL& effective_site_url) {
+#if BUILDFLAG(ENABLE_ELECTRON_EXTENSIONS)
+  return GetEnabledExtensionFromEffectiveURL(browser_context,
+                                             effective_site_url) != nullptr;
+#else
+  return content::ContentBrowserClient::DoesSiteRequireDedicatedProcess(
+      browser_context, effective_site_url);
+#endif
+}
+
 void ElectronBrowserClient::BindHostReceiverForRenderer(
     content::RenderProcessHost* render_process_host,
     mojo::GenericPendingReceiver receiver) {
diff --git a/shell/browser/electron_browser_client.h b/shell/browser/electron_browser_client.h
index 46eb0e790a..cc8cbe76b1 100644
--- a/shell/browser/electron_browser_client.h
+++ b/shell/browser/electron_browser_client.h
@@ -30,6 +30,7 @@ class FilePath;
 
 namespace content {
 class ClientCertificateDelegate;
+class NavigationHandle;
 class PlatformNotificationService;
 class NavigationThrottleRegistry;
 class QuotaPermissionContext;
@@ -82,6 +83,14 @@ class ElectronBrowserClient : public content::ContentBrowserClient,
   // content::ContentBrowserClient:
   std::string GetApplicationLocale() override;
   bool ShouldEnableStrictSiteIsolation() override;
+  bool ShouldEnableSubframeZoom() override;
+#if BUILDFLAG(ENABLE_PDF_VIEWER)
+  std::optional<network::CrossOriginEmbedderPolicy>
+  MaybeOverrideLocalURLCrossOriginEmbedderPolicy(
+      content::NavigationHandle* navigation_handle) override;
+#endif  // BUILDFLAG(ENABLE_PDF_VIEWER)
+  bool DoesSiteRequireDedicatedProcess(content::BrowserContext* browser_context,
+                                       const GURL& effective_site_url) override;
   void BindHostReceiverForRenderer(
       content::RenderProcessHost* render_process_host,
       mojo::GenericPendingReceiver receiver) override;
diff --git a/shell/browser/extensions/api/streams_private/streams_private_api.cc b/shell/browser/extensions/api/streams_private/streams_private_api.cc
index d3153b05c6..62a9848c04 100644
--- a/shell/browser/extensions/api/streams_private/streams_private_api.cc
+++ b/shell/browser/extensions/api/streams_private/streams_private_api.cc
@@ -70,7 +70,7 @@ void StreamsPrivateAPI::SendExecuteMimeTypeHandlerEvent(
       std::move(transferrable_loader), original_url);
 
 #if BUILDFLAG(ENABLE_PDF_VIEWER)
-  if (base::FeatureList::IsEnabled(chrome_pdf::features::kPdfOopif) &&
+  if (chrome_pdf::features::IsOopifPdfEnabled() &&
       extension_id == extension_misc::kPdfExtensionId) {
     pdf::PdfViewerStreamManager::Create(web_contents);
     pdf::PdfViewerStreamManager::FromWebContents(web_contents)