Reuse declutter tree for hit detection

Replaying for hit detection no longer declutters, but uses the declutter tree
from the previous rendered frame.

src/ol/renderer/canvas/vectorlayer.js

@@ -138,6 +138,9 @@ ol.renderer.canvas.VectorLayer.prototype.composeFrame = function(frameState, lay
   }
   var replayGroup = this.replayGroup_;
   if (replayGroup && !replayGroup.isEmpty()) {
+    if (this.declutterTree_) {
+      this.declutterTree_.clear();
+    }
     var layer = /** @type {ol.layer.Vector} */ (this.getLayer());
     var drawOffsetX = 0;
     var drawOffsetY = 0;
@@ -229,9 +232,6 @@ ol.renderer.canvas.VectorLayer.prototype.composeFrame = function(frameState, lay
   if (clipped) {
     context.restore();
   }
-  if (this.declutterTree_) {
-    this.declutterTree_.clear();
-  }
   this.postCompose(context, frameState, layerState, transform);
 
 };
@@ -249,7 +249,6 @@ ol.renderer.canvas.VectorLayer.prototype.forEachFeatureAtCoordinate = function(c
     var layer = /** @type {ol.layer.Vector} */ (this.getLayer());
     /** @type {Object.<string, boolean>} */
     var features = {};
-    var declutterReplays = layer.getDeclutter() ? {} : null;
     var result = this.replayGroup_.forEachFeatureAtCoordinate(coordinate, resolution,
         rotation, hitTolerance, {},
         /**
@@ -262,10 +261,7 @@ ol.renderer.canvas.VectorLayer.prototype.forEachFeatureAtCoordinate = function(c
             features[key] = true;
             return callback.call(thisArg, feature, layer);
           }
-        }, declutterReplays);
-    if (this.declutterTree_) {
-      this.declutterTree_.clear();
-    }
+        }, null);
     return result;
   }
 };

src/ol/renderer/canvas/vectortilelayer.js

@@ -270,7 +270,6 @@ ol.renderer.canvas.VectorTileLayer.prototype.forEachFeatureAtCoordinate = functi
   var rotation = frameState.viewState.rotation;
   hitTolerance = hitTolerance == undefined ? 0 : hitTolerance;
   var layer = this.getLayer();
-  var declutterReplays = layer.getDeclutter() ? {} : null;
   /** @type {Object.<string, boolean>} */
   var features = {};
 
@@ -308,12 +307,9 @@ ol.renderer.canvas.VectorTileLayer.prototype.forEachFeatureAtCoordinate = functi
               features[key] = true;
               return callback.call(thisArg, feature, layer);
             }
-          }, declutterReplays);
+          }, null);
     }
   }
-  if (this.declutterTree_) {
-    this.declutterTree_.clear();
-  }
   return found;
 };
 
@@ -387,6 +383,9 @@ ol.renderer.canvas.VectorTileLayer.prototype.postCompose = function(context, fra
     offsetY = Math.round(pixelRatio * size[1] / 2);
     ol.render.canvas.rotateAtOffset(context, -rotation, offsetX, offsetY);
   }
+  if (declutterReplays) {
+    this.declutterTree_.clear();
+  }
   var tiles = this.renderedTiles;
   var tileGrid = source.getTileGridForProjection(frameState.viewState.projection);
   var clips = [];
@@ -443,7 +442,6 @@ ol.renderer.canvas.VectorTileLayer.prototype.postCompose = function(context, fra
   }
   if (declutterReplays) {
     ol.render.canvas.ReplayGroup.replayDeclutter(declutterReplays, context, rotation);
-    this.declutterTree_.clear();
   }
   if (rotation) {
     ol.render.canvas.rotateAtOffset(context, rotation,