Document System.GCMemoryInfo (#2837)

* Document System.GCMemoryInfo

* Changed return value description.

Author: carlossanlop

xml/System/GC.xml

@@ -771,8 +771,8 @@ This method is most useful in monitoring scenarios for measuring the difference
       </ReturnValue>
       <Parameters />
       <Docs>
-        <summary>To be added.</summary>
-        <returns>To be added.</returns>
+        <summary>Gets garbage collection memory information.</summary>
+        <returns>An object that contains information about the garbage collector's memory usage.</returns>
         <remarks>To be added.</remarks>
       </Docs>
     </Member>
@@ -2053,4 +2053,4 @@ This method is most useful in monitoring scenarios for measuring the difference
       </Docs>
     </Member>
   </Members>
-</Type>
+</Type>