detect cpu feature for all x64 and x86 platforms (no longer windows only).

base/cpu.h

Index: base/cpu.h
diff --git a/base/cpu.h b/base/cpu.h
index 963da1a7b4a551d0a3f155c26b7509b27218b5e7..4e3d483ef166d1cdf3833bc4e75155c9a8556be1 100644
--- a/base/cpu.h
+++ b/base/cpu.h
@@ -6,6 +6,8 @@
 #define BASE_CPU_H_
 #pragma once
 
+#include "build/build_config.h"
+
 #include <string>
 
 namespace base {
@@ -24,6 +26,7 @@ class CPU {
   int type() const { return type_; }
   int extended_model() const { return ext_model_; }
   int extended_family() const { return ext_family_; }
+  int has_sse2() const { return has_sse2_; }
 
  private:
   // Query the processor for CPUID information.
@@ -35,6 +38,7 @@ class CPU {
   int stepping_;  // processor revision number
   int ext_model_;
   int ext_family_;
+  bool has_sse2_;
   std::string cpu_vendor_;
 };