ShapeDetection: Holding all of mock service to prevent GC

third_party/WebKit/LayoutTests/shapedetection/resources/mock-facedetection.js

 "use strict";
 
 let mockFaceDetectionProviderReady = define(
   'mockFaceDetectionProvider',
   ['services/shape_detection/public/interfaces/facedetection.mojom',
    'services/shape_detection/public/interfaces/facedetection_provider.mojom',
    'mojo/public/js/bindings',
    'mojo/public/js/core',
    'content/public/renderer/interfaces',
   ], (faceDetection, faceDetectionProvider, bindings, mojo, interfaces) => {
 
   class MockFaceDetectionProvider {
     constructor() {
       this.bindingSet_ = new bindings.BindingSet(
           faceDetectionProvider.FaceDetectionProvider);
 
       interfaces.addInterfaceOverrideForTesting(
           faceDetectionProvider.FaceDetectionProvider.name,
           handle => this.bindingSet_.addBinding(this, handle));
+
+      this.serviceArray_ = [];

[Ken Rockot(use gerrit already), 2017/05/03 16:48:54]

nit: how about "mockServiceInstances_" instead of "serviceArray_"?

+      this.buffer_data_ = [];
     }
 
     createFaceDetection(request, options) {
-      this.mock_service_ = new MockFaceDetection(request, options);
+      this.maxDetectedFaces_ = options.max_detected_faces;

[Ken Rockot(use gerrit already), 2017/05/03 16:48:54]

Doesn't this effectively cause the same problem as we have with the mock service
instances now? i.e. multiple tests may be using this provider object at the same
time and can thus trample the properties set here?

+      this.fastMode_ = options.fast_mode;
+
+      let mock_service = new MockFaceDetection(request, options, this);

[Ken Rockot(use gerrit already), 2017/05/03 16:48:54]

nit: Please either just delete this unnecessary line (inline the new at the
push() call) or fix the naming style to mockService

+      this.serviceArray_.push(mock_service);
     }
 
     getFrameData() {
-      return this.mock_service_.buffer_data_;
+      return this.buffer_data_;

[Ken Rockot(use gerrit already), 2017/05/03 16:48:54]

nit: While you're here, please fix the naming style to bufferData_.

     }
 
     getMaxDetectedFaces() {
-     return this.mock_service_.maxDetectedFaces_;
+     return this.maxDetectedFaces_;
     }
 
     getFastMode () {
-      return this.mock_service_.fastMode_;
+      return this.fastMode_;
     }
   }
 
   class MockFaceDetection {
-    constructor(request, options) {
-      this.maxDetectedFaces_ = options.max_detected_faces;
-      this.fastMode_ = options.fast_mode;
+    constructor(request, options, provider) {
+      this.provider_ = provider;
       this.binding_ = new bindings.Binding(faceDetection.FaceDetection, this,
                                            request);
     }
 
     detect(frame_data, width, height) {
       let receivedStruct = mojo.mapBuffer(frame_data, 0, width*height*4, 0);
-      this.buffer_data_ = new Uint32Array(receivedStruct.buffer);
+      this.provider_.buffer_data_ = new Uint32Array(receivedStruct.buffer);
       return Promise.resolve({
         result: {
           bounding_boxes: [
             { x : 1.0, y: 1.0, width: 100.0, height: 100.0 },
             { x : 2.0, y: 2.0, width: 200.0, height: 200.0 },
             { x : 3.0, y: 3.0, width: 300.0, height: 300.0 },
           ]
         }
       });
       mojo.unmapBuffer(receivedStruct.buffer);
     }
   }
   return new MockFaceDetectionProvider();
 });