Adds AVX detection to CPU and records a histogram of Intel uArch Support

base/cpu.h

Index: base/cpu.h
diff --git a/base/cpu.h b/base/cpu.h
index 957b1a564c9a6b23a03f9a56d1972d586240e4df..dda3295206e0eea6627ce3d73fee6d3685401f7b 100644
--- a/base/cpu.h
+++ b/base/cpu.h
@@ -32,6 +32,7 @@ class BASE_EXPORT CPU {
   bool has_ssse3() const { return has_ssse3_; }
   bool has_sse41() const { return has_sse41_; }
   bool has_sse42() const { return has_sse42_; }
+  bool has_avx() const { return has_avx_; }
   const std::string& cpu_brand() const { return cpu_brand_; }
 
  private:
@@ -51,6 +52,7 @@ class BASE_EXPORT CPU {
   bool has_ssse3_;
   bool has_sse41_;
   bool has_sse42_;
+  bool has_avx_;
   std::string cpu_vendor_;
   std::string cpu_brand_;
 };