Add a shared memory variant of CefProcessMessage (fixes issue #3126)

CefSharedProcessMessageBuilder supports creation of a CefProcessMessage
backed by a CefSharedMemoryRegion.

Performance tests comparing the existing ArgumentList approach and the new
SharedMemoryRegion approach have been added to cefclient at
http://tests/ipc_performance.

CefMessageRouter has been updated to use SharedMemoryRegion as transport
for larger message payloads. The threshold is configurable via
|CefMessageRouterConfig.message_size_threshold|.

To test:
run `ceftests --gtest_filter=SendSharedProcessMessageTest.*:SharedProcessMessageTest.*:MessageRouterTest.Threshold*`

libcef_dll/ctocpp/shared_process_message_builder_ctocpp.cc

@@ -0,0 +1,132 @@
+// Copyright (c) 2022 The Chromium Embedded Framework Authors. All rights
+// reserved. Use of this source code is governed by a BSD-style license that
+// can be found in the LICENSE file.
+//
+// ---------------------------------------------------------------------------
+//
+// This file was generated by the CEF translator tool. If making changes by
+// hand only do so within the body of existing method and function
+// implementations. See the translator.README.txt file in the tools directory
+// for more information.
+//
+// $hash=a20e093efb07503fe9e64c97c14091e3921544cd$
+//
+
+#include "libcef_dll/ctocpp/shared_process_message_builder_ctocpp.h"
+#include "libcef_dll/ctocpp/process_message_ctocpp.h"
+#include "libcef_dll/shutdown_checker.h"
+
+// STATIC METHODS - Body may be edited by hand.
+
+NO_SANITIZE("cfi-icall")
+CefRefPtr<CefSharedProcessMessageBuilder>
+CefSharedProcessMessageBuilder::Create(const CefString& name,
+                                       size_t byte_size) {
+  shutdown_checker::AssertNotShutdown();
+
+  // AUTO-GENERATED CONTENT - DELETE THIS COMMENT BEFORE MODIFYING
+
+  // Verify param: name; type: string_byref_const
+  DCHECK(!name.empty());
+  if (name.empty())
+    return nullptr;
+
+  // Execute
+  cef_shared_process_message_builder_t* _retval =
+      cef_shared_process_message_builder_create(name.GetStruct(), byte_size);
+
+  // Return type: refptr_same
+  return CefSharedProcessMessageBuilderCToCpp::Wrap(_retval);
+}
+
+// VIRTUAL METHODS - Body may be edited by hand.
+
+NO_SANITIZE("cfi-icall") bool CefSharedProcessMessageBuilderCToCpp::IsValid() {
+  shutdown_checker::AssertNotShutdown();
+
+  cef_shared_process_message_builder_t* _struct = GetStruct();
+  if (CEF_MEMBER_MISSING(_struct, is_valid))
+    return false;
+
+  // AUTO-GENERATED CONTENT - DELETE THIS COMMENT BEFORE MODIFYING
+
+  // Execute
+  int _retval = _struct->is_valid(_struct);
+
+  // Return type: bool
+  return _retval ? true : false;
+}
+
+NO_SANITIZE("cfi-icall") size_t CefSharedProcessMessageBuilderCToCpp::Size() {
+  shutdown_checker::AssertNotShutdown();
+
+  cef_shared_process_message_builder_t* _struct = GetStruct();
+  if (CEF_MEMBER_MISSING(_struct, size))
+    return 0;
+
+  // AUTO-GENERATED CONTENT - DELETE THIS COMMENT BEFORE MODIFYING
+
+  // Execute
+  size_t _retval = _struct->size(_struct);
+
+  // Return type: simple
+  return _retval;
+}
+
+NO_SANITIZE("cfi-icall") void* CefSharedProcessMessageBuilderCToCpp::Memory() {
+  shutdown_checker::AssertNotShutdown();
+
+  cef_shared_process_message_builder_t* _struct = GetStruct();
+  if (CEF_MEMBER_MISSING(_struct, memory))
+    return nullptr;
+
+  // Execute
+  void* _retval = _struct->memory(_struct);
+
+  // Return type: simple
+  return _retval;
+}
+
+NO_SANITIZE("cfi-icall")
+CefRefPtr<CefProcessMessage> CefSharedProcessMessageBuilderCToCpp::Build() {
+  shutdown_checker::AssertNotShutdown();
+
+  cef_shared_process_message_builder_t* _struct = GetStruct();
+  if (CEF_MEMBER_MISSING(_struct, build))
+    return nullptr;
+
+  // AUTO-GENERATED CONTENT - DELETE THIS COMMENT BEFORE MODIFYING
+
+  // Execute
+  cef_process_message_t* _retval = _struct->build(_struct);
+
+  // Return type: refptr_same
+  return CefProcessMessageCToCpp::Wrap(_retval);
+}
+
+// CONSTRUCTOR - Do not edit by hand.
+
+CefSharedProcessMessageBuilderCToCpp::CefSharedProcessMessageBuilderCToCpp() {}
+
+// DESTRUCTOR - Do not edit by hand.
+
+CefSharedProcessMessageBuilderCToCpp::~CefSharedProcessMessageBuilderCToCpp() {
+  shutdown_checker::AssertNotShutdown();
+}
+
+template <>
+cef_shared_process_message_builder_t*
+CefCToCppRefCounted<CefSharedProcessMessageBuilderCToCpp,
+                    CefSharedProcessMessageBuilder,
+                    cef_shared_process_message_builder_t>::
+    UnwrapDerived(CefWrapperType type, CefSharedProcessMessageBuilder* c) {
+  NOTREACHED() << "Unexpected class type: " << type;
+  return nullptr;
+}
+
+template <>
+CefWrapperType
+    CefCToCppRefCounted<CefSharedProcessMessageBuilderCToCpp,
+                        CefSharedProcessMessageBuilder,
+                        cef_shared_process_message_builder_t>::kWrapperType =
+        WT_SHARED_PROCESS_MESSAGE_BUILDER;