[turbolizer]: Fix bugs

tools/turbolizer/graph-view.js

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 "use strict";
 
 class GraphView extends View {
   constructor (d3, id, nodes, edges, broker) {
     super(id, broker);
     var graph = this;
@@ skipping 553 matching lines @@
           frontier.each(function(n) {
             state.selection.select(this, true);
           });
         }
         graph.updateGraphVisibility();
       }
       allowRepetition = false;
     }
 
     var allowRepetition = true;
+    var eventHandled = true; // unless the below switch defaults
     switch(d3.event.keyCode) {
     case 49:
     case 50:
     case 51:
     case 52:
     case 53:
     case 54:
     case 55:
     case 56:
     case 57:
@@ skipping 25 matching lines @@
     case 65:
       // 'a'
       graph.selectAllNodes();
       allowRepetition = false;
       break;
     case 38:
     case 40: {
       selectNodesThroughEdges(d3.event.keyCode == 38, undefined, true);
       break;
     }
+    default:
+      eventHandled = false;
+      break;
+    }
+    if (eventHandled) {
+      d3.event.preventDefault();
     }
     if (!allowRepetition) {
       state.lastKeyDown = d3.event.keyCode;
     }
   }
 
   svgKeyUp() {
     this.state.lastKeyDown = -1
   };
 
@@ skipping 343 matching lines @@
   }
 
   viewWholeGraph() {
     var graph = this;
     var minScale = graph.minScale();
     var translation = [0, 0];
     translation = graph.getVisibleTranslation(translation, minScale);
     graph.translateClipped(translation, minScale);
   }
 }