Make new WebUSB implementation more resilient to garbage collection.

third_party/WebKit/Source/modules/webusb/USB.cpp

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "modules/webusb/USB.h"
 
 #include "bindings/core/v8/ScriptPromise.h"
 #include "bindings/core/v8/ScriptPromiseResolver.h"
 #include "core/dom/DOMException.h"
 #include "core/dom/Document.h"
@@ skipping 42 matching lines @@
     ExecutionContext* context = resolver->getExecutionContext();
     return context && !context->activeDOMObjectsAreStopped();
 }
 
 } // namespace
 
 USB::USB(LocalFrame& frame)
     : ContextLifecycleObserver(frame.document())
 {
     frame.serviceRegistry()->connectToRemoteService(mojo::GetProxy(&m_deviceManager));
-    m_deviceManager.set_connection_error_handler([this]() {
-        m_deviceManager.reset();
-        for (ScriptPromiseResolver* resolver : m_deviceManagerRequests) {
-            if (isActive(resolver))
-                resolver->reject(DOMException::create(NotFoundError, kNoServiceError));
-        }
-        m_deviceManagerRequests.clear();
-    });
+    m_deviceManager.set_connection_error_handler(createBaseCallback(bind(&USB::onDeviceManagerConnectionError, WeakPersistentThisPointer<USB>(this))));
     // Set up two sequential calls to GetDeviceChanges to avoid latency.
-    m_deviceManager->GetDeviceChanges(createBaseCallback(bind<usb::DeviceChangeNotificationPtr>(&USB::onDeviceChanges, this)));
-    m_deviceManager->GetDeviceChanges(createBaseCallback(bind<usb::DeviceChangeNotificationPtr>(&USB::onDeviceChanges, this)));
+    m_deviceManager->GetDeviceChanges(createBaseCallback(bind<usb::DeviceChangeNotificationPtr>(&USB::onDeviceChanges, WeakPersistentThisPointer<USB>(this))));
+    m_deviceManager->GetDeviceChanges(createBaseCallback(bind<usb::DeviceChangeNotificationPtr>(&USB::onDeviceChanges, WeakPersistentThisPointer<USB>(this))));
 }
 
 USB::~USB()
 {
-    DCHECK(!m_deviceManager);
+    // |m_deviceManager| and |m_chooserService| may still be valid but there
+    // should be no more outstanding requests to them because each holds a
+    // persistent handle to this object.
     DCHECK(m_deviceManagerRequests.isEmpty());
-    DCHECK(!m_chooserService);
     DCHECK(m_chooserServiceRequests.isEmpty());
 }
 
 ScriptPromise USB::getDevices(ScriptState* scriptState)
 {
     ScriptPromiseResolver* resolver = ScriptPromiseResolver::create(scriptState);
     ScriptPromise promise = resolver->promise();
     if (!m_deviceManager) {
         resolver->reject(DOMException::create(NotSupportedError));
     } else {
@@ skipping 13 matching lines @@
     ScriptPromiseResolver* resolver = ScriptPromiseResolver::create(scriptState);
     ScriptPromise promise = resolver->promise();
 
     if (!m_chooserService) {
         LocalFrame* frame = getExecutionContext() ? toDocument(getExecutionContext())->frame() : nullptr;
         if (!frame) {
             resolver->reject(DOMException::create(NotSupportedError));
             return promise;
         }
         frame->serviceRegistry()->connectToRemoteService(mojo::GetProxy(&m_chooserService));
-        m_chooserService.set_connection_error_handler([this]() {
-            m_chooserService.reset();
-            for (ScriptPromiseResolver* resolver : m_chooserServiceRequests) {
-                if (isActive(resolver))
-                    resolver->reject(DOMException::create(NotFoundError, kNoServiceError));
-            }
-            m_chooserServiceRequests.clear();
-        });
+        m_chooserService.set_connection_error_handler(createBaseCallback(bind(&USB::onChooserServiceConnectionError, WeakPersistentThisPointer<USB>(this))));
     }
 
     String errorMessage;
     if (!scriptState->getExecutionContext()->isSecureContext(errorMessage)) {
         resolver->reject(DOMException::create(SecurityError, errorMessage));
     } else if (!UserGestureIndicator::consumeUserGesture()) {
         resolver->reject(DOMException::create(SecurityError, "Must be handling a user gesture to show a permission request."));
     } else {
         Vector<usb::DeviceFilterPtr> filters;
         if (options.hasFilters()) {
@@ skipping 49 matching lines @@
         usb::DevicePtr device;
         m_deviceManager->GetDevice(deviceInfo->guid, mojo::GetProxy(&device));
         resolver->resolve(USBDevice::create(std::move(deviceInfo), std::move(device), resolver->getExecutionContext()));
     } else {
         resolver->reject(DOMException::create(NotFoundError, "No device selected."));
     }
 }
 
 void USB::onDeviceChanges(usb::DeviceChangeNotificationPtr notification)
 {
-    m_deviceManager->GetDeviceChanges(createBaseCallback(bind<usb::DeviceChangeNotificationPtr>(&USB::onDeviceChanges, this)));
+    m_deviceManager->GetDeviceChanges(createBaseCallback(bind<usb::DeviceChangeNotificationPtr>(&USB::onDeviceChanges, WeakPersistentThisPointer<USB>(this))));
     for (auto& deviceInfo : notification->devices_added.PassStorage()) {
         usb::DevicePtr device;
         m_deviceManager->GetDevice(deviceInfo->guid, mojo::GetProxy(&device));
         dispatchEvent(USBConnectionEvent::create(EventTypeNames::connect, USBDevice::create(std::move(deviceInfo), std::move(device), getExecutionContext())));
     }
     for (auto& deviceInfo : notification->devices_removed.PassStorage())
         dispatchEvent(USBConnectionEvent::create(EventTypeNames::disconnect, USBDevice::create(std::move(deviceInfo), nullptr, getExecutionContext())));
 }
 
+void USB::onDeviceManagerConnectionError()
+{
+    m_deviceManager.reset();
+    for (ScriptPromiseResolver* resolver : m_deviceManagerRequests) {

[esprehn, 2016/04/23 00:54:02]

seems like this needs to be more centralized, doing this in every subsystem is
bad.

+        if (isActive(resolver))
+            resolver->reject(DOMException::create(NotFoundError, kNoServiceError));
+    }
+    m_deviceManagerRequests.clear();
+}
+
+void USB::onChooserServiceConnectionError()
+{
+    m_chooserService.reset();
+    for (ScriptPromiseResolver* resolver : m_chooserServiceRequests) {
+        if (isActive(resolver))
+            resolver->reject(DOMException::create(NotFoundError, kNoServiceError));
+    }
+    m_chooserServiceRequests.clear();
+}
+
 DEFINE_TRACE(USB)
 {
     EventTargetWithInlineData::trace(visitor);
     ContextLifecycleObserver::trace(visitor);
     visitor->trace(m_deviceManagerRequests);
     visitor->trace(m_chooserServiceRequests);
 }
 
 } // namespace blink