Create a field trial to test if we can detect good QPC implementations.

base/cpu.h

Index: base/cpu.h
diff --git a/base/cpu.h b/base/cpu.h
index 65fda47950c9dae97dcd9a288d3d65c2affac79b..d929370cce388fa747fb88737ddeef52cdf6123c 100644
--- a/base/cpu.h
+++ b/base/cpu.h
@@ -45,6 +45,7 @@ class BASE_EXPORT CPU {
   bool has_sse41() const { return has_sse41_; }
   bool has_sse42() const { return has_sse42_; }
   bool has_avx() const { return has_avx_; }
+  bool has_nonstoptsc() const { return has_nonstoptsc_; }
   IntelMicroArchitecture GetIntelMicroArchitecture() const;
   const std::string& cpu_brand() const { return cpu_brand_; }
 
@@ -66,6 +67,7 @@ class BASE_EXPORT CPU {
   bool has_sse41_;
   bool has_sse42_;
   bool has_avx_;
+  bool has_nonstoptsc_;
   std::string cpu_vendor_;
   std::string cpu_brand_;
 };