[tracing] Navigate to parent node in heap dump UI upon pressing backspace

tracing/tracing/ui/analysis/memory_dump_heap_details_breakdown_view.html

Index: tracing/tracing/ui/analysis/memory_dump_heap_details_breakdown_view.html
diff --git a/tracing/tracing/ui/analysis/memory_dump_heap_details_breakdown_view.html b/tracing/tracing/ui/analysis/memory_dump_heap_details_breakdown_view.html
index c98f9840ee6e07d44c90be1491817464f85eeeb9..55e74094468d2ca89baa2d64a92748624a181775 100644
--- a/tracing/tracing/ui/analysis/memory_dump_heap_details_breakdown_view.html
+++ b/tracing/tracing/ui/analysis/memory_dump_heap_details_breakdown_view.html
@@ -52,6 +52,7 @@ tr.exportTo('tr.ui.analysis', function() {
 
     ready: function() {
       this.scheduleRebuild_();
+      this.root.addEventListener('keydown', this.onKeyDown_.bind(this), true);
     },
 
     get displayedNode() {
@@ -108,6 +109,21 @@ tr.exportTo('tr.ui.analysis', function() {
         this.$.tabs.label = 'Break selected node further by:';
       else
         this.$.tabs.label = 'Selected node cannot be broken down any further.';
+    },
+
+    onKeyDown_: function(keyEvent) {
+      if (keyEvent.keyCode !== 8 /* backspace */)
+        return;
+      if (!this.displayedNode_ || !this.displayedNode_.parentNode)
+        return;
+
+      // Enter the parent node upon pressing backspace.
+      var viewEvent = new tr.b.Event('enter-node');
+      viewEvent.node = this.displayedNode_.parentNode;
+      this.dispatchEvent(viewEvent);
+
+      keyEvent.stopPropagation();
+      keyEvent.preventDefault();
     }
   });