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*`

tests/shared/common/binary_value_utils.cc

@@ -0,0 +1,44 @@
+// 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.
+
+#include "tests/shared/common/binary_value_utils.h"
+
+namespace bv_utils {
+
+const char kTestSendProcessMessage[] = "testSendProcessMessage";
+const char kTestSendSMRProcessMessage[] = "testSendSMRProcessMessage";
+
+TimePoint Now() {
+  return std::chrono::high_resolution_clock::now();
+}
+
+CefRefPtr<CefBinaryValue> CreateCefBinaryValue(
+    const std::vector<uint8_t>& data) {
+  return CefBinaryValue::Create(data.data(), data.size());
+}
+
+RendererMessage GetRendererMsgFromBinary(
+    const CefRefPtr<CefBinaryValue>& value) {
+  DCHECK_GE(value->GetSize(), sizeof(RendererMessage));
+  std::vector<uint8_t> data(value->GetSize());
+  value->GetData(data.data(), data.size(), 0);
+  return *reinterpret_cast<const RendererMessage*>(data.data());
+}
+
+BrowserMessage GetBrowserMsgFromBinary(const CefRefPtr<CefBinaryValue>& value) {
+  DCHECK_GE(value->GetSize(), sizeof(BrowserMessage));
+  std::vector<uint8_t> data(value->GetSize());
+  value->GetData(data.data(), data.size(), 0);
+  return *reinterpret_cast<const BrowserMessage*>(data.data());
+}
+
+std::string ToMilliString(const Duration& duration) {
+  const auto ms =
+      std::chrono::duration_cast<std::chrono::duration<double, std::milli>>(
+          duration);
+
+  return std::to_string(ms.count());
+}
+
+}  // namespace bv_utils