Add histograms to compare GetVersionEx() with VerQueryValue() of kernel32

base/win/windows_version.h

Index: base/win/windows_version.h
diff --git a/base/win/windows_version.h b/base/win/windows_version.h
index 676bd979578b9fc07b83bed55d6d5257650858c8..7bc8b6fe560f5099ea6dec51b811d86d5b01eb4c 100644
--- a/base/win/windows_version.h
+++ b/base/win/windows_version.h
@@ -21,17 +21,20 @@ namespace win {
 // syntactic sugar reasons; see the declaration of GetVersion() below.
 // NOTE: Keep these in order so callers can do things like
 // "if (base::win::GetVersion() >= base::win::VERSION_VISTA) ...".
+//
+// This enum is used in metrics histograms, so they shouldn't be reordered or
+// removed. New values can be added before VERSION_WIN_LAST.
 enum Version {
   VERSION_PRE_XP = 0,  // Not supported.
-  VERSION_XP,
-  VERSION_SERVER_2003,  // Also includes XP Pro x64 and Server 2003 R2.
-  VERSION_VISTA,        // Also includes Windows Server 2008.
-  VERSION_WIN7,         // Also includes Windows Server 2008 R2.
-  VERSION_WIN8,         // Also includes Windows Server 2012.
-  VERSION_WIN8_1,       // Also includes Windows Server 2012 R2.
-  VERSION_WIN10,        // Also includes Windows 10 Server.
-  VERSION_WIN10_TH2,    // Threshold 2: Version 1511, Build 10586.
-  VERSION_WIN_LAST,     // Indicates error condition.
+  VERSION_XP = 1,
+  VERSION_SERVER_2003 = 2,  // Also includes XP Pro x64 and Server 2003 R2.
+  VERSION_VISTA = 3,        // Also includes Windows Server 2008.
+  VERSION_WIN7 = 4,         // Also includes Windows Server 2008 R2.
+  VERSION_WIN8 = 5,         // Also includes Windows Server 2012.
+  VERSION_WIN8_1 = 6,       // Also includes Windows Server 2012 R2.
+  VERSION_WIN10 = 7,        // Also includes Windows 10 Server.
+  VERSION_WIN10_TH2 = 8,    // Threshold 2: Version 1511, Build 10586.
+  VERSION_WIN_LAST,         // Indicates error condition.
 };
 
 // A rough bucketing of the available types of versions of Windows. This is used
@@ -86,6 +89,7 @@ class BASE_EXPORT OSInfo {
   static OSInfo* GetInstance();
 
   Version version() const { return version_; }
+  Version Kernel32Version() const;
   // The next two functions return arrays of values, [major, minor(, build)].
   VersionNumber version_number() const { return version_number_; }
   VersionType version_type() const { return version_type_; }
@@ -105,6 +109,8 @@ class BASE_EXPORT OSInfo {
   ~OSInfo();
 
   Version version_;
+  mutable Version kernel32_version_;
+  mutable bool got_kernel32_version_;
   VersionNumber version_number_;
   VersionType version_type_;
   ServicePack service_pack_;