UMA: Set Hardware model class on Mac.

base/sys_info.h

Index: base/sys_info.h
diff --git a/base/sys_info.h b/base/sys_info.h
index d24acdf6b434eddf991c7787dc4f4e10989e9003..2e490f9ebd3274835e2488b2bc98a9ad1e600935 100644
--- a/base/sys_info.h
+++ b/base/sys_info.h
@@ -51,6 +51,10 @@ class BASE_EXPORT SysInfo {
   // Returns system uptime in milliseconds.
   static int64 Uptime();
 
+  // Returns a descriptive string for the current machine model or "Unknown"

[Alexei Svitkine (slow), 2014/11/04 16:22:12]

Maybe better to return an empty string if unknown?

[jeremy, 2014/11/05 05:38:06]

Done.

+  // if an error occured.

[Alexei Svitkine (slow), 2014/11/04 16:22:12]

Can you provide an example of a return value in the comment?

Also, mention which platforms it's implemented on.

[jeremy, 2014/11/05 05:38:06]

Example added.
I've never seen us mention supported platforms in a header comment before - if
you think I should, I have no problem adding it :)

[Alexei Svitkine (slow), 2014/11/05 15:47:21]

My preference would be to add it - as it's helpful to users of the API when
they're looking at the header file. Less surprises, etc.

+  static std::string HardwareModelName();
+
   // Returns the name of the host operating system.
   static std::string OperatingSystemName();