CoreCLR: Automatically port System.GC* triple slash comments to Docs (#2759)

* CoreCLR: Automatically port System.GC* triple slash comments to Docs

* Add return for GetTotalAllocatedBytes

* Fix some values

* GCMemoryInfo summary

* Update GC.xml

* Update GCMemoryInfo.xml

Author: carlossanlop

xml/System/GC.xml

@@ -929,9 +929,9 @@ This method is most useful in monitoring scenarios for measuring the difference
         <Parameter Name="precise" Type="System.Boolean" Index="0" FrameworkAlternate="netcore-3.0" />
       </Parameters>
       <Docs>
-        <param name="precise">To be added.</param>
-        <summary>To be added.</summary>
-        <returns>To be added.</returns>
+        <param name="precise">If <see langword="true" />, gather a precise number; otherwise, gather an approximate count. Gathering a precise value entails a significant performance penalty.</param>
+        <summary>Gets a count of the bytes allocated over the lifetime of the process.</summary>
+        <returns>The total number of bytes allocated over the lifetime of the process.</returns>
         <remarks>To be added.</remarks>
       </Docs>
     </Member>

xml/System/GCMemoryInfo.xml

@@ -19,7 +19,7 @@
     </Attribute>
   </Attributes>
   <Docs>
-    <summary>To be added.</summary>
+    <summary>Provides a set of APIs that can be used to retrieve garbage collection information.</summary>
     <remarks>To be added.</remarks>
   </Docs>
   <Members>
@@ -39,9 +39,27 @@
         <ReturnType>System.Int64</ReturnType>
       </ReturnValue>
       <Docs>
-        <summary>To be added.</summary>
-        <value>To be added.</value>
-        <remarks>To be added.</remarks>
+        <summary>Gets the total fragmentation when the last garbage collection occurred.</summary>
+        <value>An integer representing the total fragmentation when the last garbage collection occurred.</value>
+        <remarks>
+          <format type="text/markdown"><![CDATA[
+
+## Remarks
+
+For example, the application has the following five objects:
+
+`| OBJ_A |     OBJ_B     | OBJ_C |   OBJ_D   | OBJ_E |`
+            
+If `OBJ_B`, `OBJ_C`, and `OBJ_E` are garbage collected but the heap is not compacted, the resulting heap will look like the following:
+
+`| OBJ_A |           F           |   OBJ_D   |`
+            
+The memory between `OBJ_A` and `OBJ_D`, which is marked `F`, is considered part of the `FragmentedBytes` and is used to allocate new objects.
+
+The memory after `OBJ_D` is not considered part of the `FragmentedBytes` but will also be used to allocate new objects.
+
+          ]]></format>
+        </remarks>
       </Docs>
     </Member>
     <Member MemberName="HeapSizeBytes">
@@ -60,8 +78,8 @@
         <ReturnType>System.Int64</ReturnType>
       </ReturnValue>
       <Docs>
-        <summary>To be added.</summary>
-        <value>To be added.</value>
+        <summary>Gets the total heap size when the last garbage collection occurred.</summary>
+        <value>The total heap size, in bytes, when the last garbage collection occurred.</value>
         <remarks>To be added.</remarks>
       </Docs>
     </Member>
@@ -81,8 +99,8 @@
         <ReturnType>System.Int64</ReturnType>
       </ReturnValue>
       <Docs>
-        <summary>To be added.</summary>
-        <value>To be added.</value>
+        <summary>Gets the high memory load threshold when the last garbage collection occured.</summary>
+        <value>The high memory load threshold, in bytes, when the last garbage collection occured.</value>
         <remarks>To be added.</remarks>
       </Docs>
     </Member>
@@ -102,8 +120,8 @@
         <ReturnType>System.Int64</ReturnType>
       </ReturnValue>
       <Docs>
-        <summary>To be added.</summary>
-        <value>To be added.</value>
+        <summary>Gets the memory load when the last garbage collection occurred.</summary>
+        <value>The memory load when the last garbage collection occurred.</value>
         <remarks>To be added.</remarks>
       </Docs>
     </Member>
@@ -123,10 +141,22 @@
         <ReturnType>System.Int64</ReturnType>
       </ReturnValue>
       <Docs>
-        <summary>To be added.</summary>
-        <value>To be added.</value>
-        <remarks>To be added.</remarks>
+        <summary>Gets the total available memory for the garbage collector to use when the last garbage collection occurred.</summary>
+        <value>The total available memory, in bytes, for the garbage collector to use when the last garbage collection occurred.</value>
+        <remarks>
+          <format type="text/markdown"><![CDATA[
+
+## Remarks
+
+This property value will be the value of the `COMPlus_GCHeapHardLimit` environment variable, or the `Server.GC.HeapHardLimit` value in `runtimeconfig.json`, if either is set.
+
+If the program is run in a container, this value is an implementation-defined fraction of the container's size.
+
+Otherwise, the value of the property is the physical memory on the machine that was available for the garbage collector to use when the last garbage collection occurred.
+
+          ]]></format>
+        </remarks>
       </Docs>
     </Member>
   </Members>
-</Type>
+</Type>