Add the context-padding parameter to the comment context

This parameter allows padding the context lines with extra lines before
and after the comment range. This parameter works only if the
enable-context parameter is set to true.

This change is backward compatible: if the new parameter is not set or
set to zero, only the lines of the comment range are returned.

Change-Id: I2d44fb852c68ba484cbf94adff912b7ee522f9c5

java/com/google/gerrit/extensions/api/changes/ChangeApi.java

@@ -413,6 +413,7 @@ public interface ChangeApi {
 
   abstract class CommentsRequest {
     private boolean enableContext;
+    private int contextPadding;
 
     /**
      * Get all published comments on a change.
@@ -436,6 +437,11 @@ public interface ChangeApi {
       return this;
     }
 
+    public CommentsRequest contextPadding(int contextPadding) {
+      this.contextPadding = contextPadding;
+      return this;
+    }
+
     public CommentsRequest withContext() {
       this.enableContext = true;
       return this;
@@ -444,6 +450,10 @@ public interface ChangeApi {
     public boolean getContext() {
       return enableContext;
     }
+
+    public int getContextPadding() {
+      return contextPadding;
+    }
   }
 
   abstract class SuggestedReviewersRequest {