Report Windows build and patch number in the component updater checks.

base/win/windows_version.cc

Index: base/win/windows_version.cc
diff --git a/base/win/windows_version.cc b/base/win/windows_version.cc
index 3cf22d8ccdad71f77da35d1310b9b73b7ede46da..39e72721b191c39619a7b24691e8c72214afc189 100644
--- a/base/win/windows_version.cc
+++ b/base/win/windows_version.cc
@@ -83,6 +83,28 @@ Version GetVersionFromKernel32() {
   return VERSION_WIN_LAST;
 }
 
+// Returns the the "UBR" value from the registry. Introduced in Windows 10,
+// this undocumented value appears to be similar to a patch number.
+// Returns 0 if the value does not exist or it could not be read.
+int GetUBR() {
+  // The values under the CurrentVersion registry hive are mirrored under
+  // the corresponding Wow6432 hive.
+  constexpr wchar_t kRegKeyWindowsNTCurrentVersion[] =

[grt (UTC plus 2), 2016/11/15 20:59:09]

"static constexpr ..." so that the string isn't pushed onto the stack.

[Sorin Jianu, 2016/11/15 23:03:29]

Done.

This had a massive impact, which I admit I did not expect. I expected that in
both cases, with and without static, the code will use the address of the string
literals and not push anything that is not needed on the stack. Effectively, I
expected the local variables to be optimized out, especially in the constexpr
case.

That did not happen in the optimized build I inspected. 

With static constexpr, the entire function is inlined. With just the constexpr
declaration, the function is not optimized, the local variables are not pushed
onto the stack but there are some streaming XMM instructions moving strings
around, which I don't understand.

+      L"SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion";
+  constexpr wchar_t kRegValUBR[] = L"UBR";
+
+  base::win::RegKey key;
+  if (key.Open(HKEY_LOCAL_MACHINE, kRegKeyWindowsNTCurrentVersion,
+               KEY_QUERY_VALUE) != ERROR_SUCCESS) {
+    return 0;
+  }
+
+  DWORD ubr = 0;
+  key.ReadValueDW(kRegValUBR, &ubr);

[grt (UTC plus 2), 2016/11/15 20:59:09]

nit: i would use L"UBR" directly here since using a local var neither reduces
wrapping nor avoids repetition of the value. i would likely keep
kRegKeyWindowsNTCurrentVersion as-is since it may avoid linewrapping.

[Sorin Jianu, 2016/11/15 23:03:29]

Done.

+
+  return static_cast<int>(ubr);
+}
+
 }  // namespace
 
 // static
@@ -112,6 +134,7 @@ OSInfo::OSInfo()
   version_number_.major = version_info.dwMajorVersion;
   version_number_.minor = version_info.dwMinorVersion;
   version_number_.build = version_info.dwBuildNumber;
+  version_number_.patch = GetUBR();
   version_ = MajorMinorBuildToVersion(
       version_number_.major, version_number_.minor, version_number_.build);
   service_pack_.major = version_info.wServicePackMajor;