Adds user agent to LibAssistant internal config.

Setting user agent via InternalOptions is deprecated in LibAssistant
1.42s. Prior to upreving LibAssistant we need to set user agent via
internal config.

A follow up CL will remove the code which sets user agent via
InternalOptions and we will uprev that change in tandem with upreving
the 1.42s changes to avoid breaking the public build.

Bug: b:138583234
Change-Id: I110a7f16ea53f38eaeac7f7065e628f7eec1ffc5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1724829Reviewed-by: Xiaohui Chen <xiaohuic@chromium.org>
Commit-Queue: David Black <dmblack@google.com>
Cr-Commit-Position: refs/heads/master@{#681886}

chromeos/services/assistant/utils.cc

@@ -11,8 +11,10 @@
 #include "base/json/json_writer.h"
 #include "base/logging.h"
 #include "base/path_service.h"
+#include "base/strings/stringprintf.h"
 #include "base/system/sys_info.h"
 #include "base/values.h"
+#include "build/util/webkit_version.h"
 #include "chromeos/assistant/internal/internal_constants.h"
 #include "chromeos/constants/chromeos_switches.h"
 #include "chromeos/dbus/util/version_loader.h"
@@ -21,6 +23,21 @@
 namespace chromeos {
 namespace assistant {
 
+namespace {
+
+void CreateUserAgent(std::string* user_agent) {
+  DCHECK(user_agent->empty());
+  base::StringAppendF(user_agent,
+                      "Mozilla/5.0 (X11; CrOS %s %s; %s) "
+                      "AppleWebKit/%d.%d (KHTML, like Gecko)",
+                      base::SysInfo::OperatingSystemArchitecture().c_str(),
+                      base::SysInfo::OperatingSystemVersion().c_str(),
+                      base::SysInfo::GetLsbReleaseBoard().c_str(),
+                      WEBKIT_VERSION_MAJOR, WEBKIT_VERSION_MINOR);
+}
+
+}  // namespace
+
 // Get the root path for assistant files.
 base::FilePath GetRootPath() {
   base::FilePath home_dir;
@@ -53,6 +70,10 @@ std::string CreateLibAssistantConfig() {
   Value internal(Type::DICTIONARY);
   internal.SetKey("surface_type", Value("OPA_CROS"));
 
+  std::string user_agent;
+  CreateUserAgent(&user_agent);
+  internal.SetKey("user_agent", Value(user_agent));
+
   // Prevent LibAssistant from automatically playing ready message TTS during
   // the startup sequence when the version of LibAssistant has been upgraded.
   internal.SetKey("override_ready_message", Value(true));