Prepend starboard OS name in user-agent string

The current OS name in user-agent string is fetched using
chromium code which just return "Linux". This misses the real
OS name for starboard platform and result in YTS test failure.
So OS name in user-agent string should include the starboard platform
OS name.

Bug: 475670748

Author: Santosh Mahto

base/system/sys_info_starboard.cc

@@ -78,6 +78,11 @@ std::string SbSysInfo::Brand() {
   __system_property_get("ro.product.brand", brand_str);
   return std::string(brand_str);
 }
+
+std::string SbSysInfo::OSFriendlyName() {
+  return "AOSP";
+}
+
 #elif BUILDFLAG(IS_STARBOARD)
 std::string SbSysInfo::OriginalDesignManufacturer() {
   return GetSystemPropertyString(kSbSystemPropertySystemIntegratorName);
@@ -95,6 +100,10 @@ std::string SbSysInfo::Brand() {
   return GetSystemPropertyString(kSbSystemPropertyBrandName);
 }
 
+std::string SbSysInfo::OSFriendlyName() {
+  return GetSystemPropertyString(kSbSystemPropertyFriendlyName);
+}
+
 #elif BUILDFLAG(IS_IOS_TVOS)
 std::string SbSysInfo::OriginalDesignManufacturer() {
   // Cobalt 25: https://github.com/youtube/cobalt/blob/62c2380b7eb0da5889a387c4b9be283656a8575d/starboard/shared/uikit/system_get_property.mm#L126
@@ -152,6 +161,10 @@ std::string SbSysInfo::Brand() {
   return "Apple";
 }
 
+std::string SbSysInfo::OSFriendlyName() {
+  SB_NOTIMPLEMENTED();
+}
+
 #endif  // BUILDFLAG(IS_ANDROID)
 
 }  // namespace starboard

base/system/sys_info_starboard.h

@@ -31,9 +31,11 @@ class BASE_EXPORT SbSysInfo {
   static std::string ModelYear();
 
   static std::string Brand();
+
+  static std::string OSFriendlyName();
 };
 
 }  // namespace starboard
 }  // namespace base
 
-#endif  // BASE_SYSTEM_SYS_INFO_STARBOARD_H_
+#endif  // BASE_SYSTEM_SYS_INFO_STARBOARD_H_

cobalt/browser/user_agent/user_agent_platform_info.cc

@@ -190,7 +190,12 @@ void UserAgentPlatformInfo::InitializePlatformDependentFieldsAndroid() {
 }
 #elif BUILDFLAG(IS_STARBOARD)
 void UserAgentPlatformInfo::InitializePlatformDependentFieldsStarboard() {
-  const std::string os_name = base::SysInfo::OperatingSystemName();
+  std::string os_name = base::SysInfo::OperatingSystemName();
+  const std::string os_friendly_name =
+      base::starboard::SbSysInfo::OSFriendlyName();
+  if (!os_friendly_name.empty()) {
+    os_name = os_friendly_name + "; " + os_name;
+  }
   const std::string os_version = base::SysInfo::OperatingSystemVersion();
   set_os_name_and_version(
       base::StringPrintf("%s %s", os_name.c_str(), os_version.c_str()));