Ranged highlights: initial commit

- Initial commit: structure, 'enabled' property controls sample
mouseDown handler.
- Minimal integration: isRangeSelected
- Minimal test.

Change-Id: I963ac7b158d57a1c24ee302d99eb6af26b0aeeeb
diff --git a/polygerrit-ui/app/elements/diff/gr-diff/gr-diff.html b/polygerrit-ui/app/elements/diff/gr-diff/gr-diff.html
index 7c66bf1..e0d003e 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff/gr-diff.html
+++ b/polygerrit-ui/app/elements/diff/gr-diff/gr-diff.html
@@ -19,6 +19,7 @@
 <link rel="import" href="../../shared/gr-rest-api-interface/gr-rest-api-interface.html">
 <link rel="import" href="../gr-diff-builder/gr-diff-builder.html">
 <link rel="import" href="../gr-diff-comment-thread/gr-diff-comment-thread.html">
+<link rel="import" href="../gr-diff-highlight/gr-diff-highlight.html">
 <link rel="import" href="../gr-diff-selection/gr-diff-selection.html">
 
 <dom-module id="gr-diff">
@@ -142,14 +143,20 @@
     <div class$="[[_computeContainerClass(_loggedIn, viewMode)]]"
         on-tap="_handleTap">
       <gr-diff-selection>
-        <gr-diff-builder
-            id="diffBuilder"
-            view-mode="[[viewMode]]"
-            is-image-diff="[[isImageDiff]]"
-            base-image="[[_baseImage]]"
-            revision-image="[[_revisionImage]]">
-          <table id="diffTable"></table>
-        </gr-diff-builder>
+        <gr-diff-highlight
+            id="highlights"
+            logged-in="[[_loggedIn]]"
+            enabled="[[hasRangedComments]]"
+            comments="[[_comments]]">
+          <gr-diff-builder
+              id="diffBuilder"
+              view-mode="[[viewMode]]"
+              is-image-diff="[[isImageDiff]]"
+              base-image="[[_baseImage]]"
+              revision-image="[[_revisionImage]]">
+            <table id="diffTable"></table>
+          </gr-diff-builder>
+        </gr-diff-highlight>
       </gr-diff-selection>
     </div>
     <gr-rest-api-interface id="restAPI"></gr-rest-api-interface>