Convert files to typescript

The change converts the following files to typescript:

* elements/diff/gr-diff-builder/gr-diff-builder-element.ts

Change-Id: Ic28adbe27eb2707427911cc1f956ed312689b160
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-processor/gr-diff-processor.ts b/polygerrit-ui/app/elements/diff/gr-diff-processor/gr-diff-processor.ts
index 74164a8..0ac39f0 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-processor/gr-diff-processor.ts
+++ b/polygerrit-ui/app/elements/diff/gr-diff-processor/gr-diff-processor.ts
@@ -48,7 +48,7 @@
   keyLocation: boolean;
 }
 
-interface KeyLocations {
+export interface KeyLocations {
   left: {[key: string]: boolean};
   right: {[key: string]: boolean};
 }