Refine systemInfo.cpu API defintions and provide systemInfo.cpu.get impl for Windows and Linux

base/sys_info_win.cc

Index: base/sys_info_win.cc
diff --git a/base/sys_info_win.cc b/base/sys_info_win.cc
index 87ce66d82b5c75deeac08875bd1aa3fddbf394dd..d8de7363c23935af1af763c875a898d82dd2daa3 100644
--- a/base/sys_info_win.cc
+++ b/base/sys_info_win.cc
@@ -80,6 +80,11 @@ std::string SysInfo::CPUArchitecture() {
 }
 
 // static
+std::string SysInfo::CPUModelName() {
+  return win::OSInfo::GetInstance()->processor_model_name();
+}
+
+// static
 size_t SysInfo::VMAllocationGranularity() {
   return win::OSInfo::GetInstance()->allocation_granularity();
 }