void DocumentThreadableLoader::handleSuccessfulFinish(unsigned long identifier, double finishTime)
{
    ASSERT(m_fallbackRequestForServiceWorker.isNull());

    if (!m_actualRequest.isNull()) {
        // FIXME: Timeout should be applied to whole fetch, not for each of
        // preflight and actual request.
        m_timeoutTimer.stop();
        ASSERT(!m_sameOriginRequest);
        ASSERT(m_options.crossOriginRequestPolicy == UseAccessControl);
        loadActualRequest();
        return;
    }

    ThreadableLoaderClient* client = m_client;
    m_client = 0;
    // Don't clear the resource as the client may need to access the downloaded
    // file which will be released when the resource is destoryed.
    if (m_async) {
        m_timeoutTimer.stop();
        m_requestStartedSeconds = 0.0;
    }
    client->didFinishLoading(identifier, finishTime);
    // |this| may be dead here in async mode.
}

void DocumentThreadableLoader::redirectBlocked()
{
    // Tells the client that a redirect was received but not followed (for an unknown reason).
    ThreadableLoaderClient* client = m_client;
    clear();
    client->didFailRedirectCheck();
    // |this| may be dead here
}

void DocumentThreadableLoader::handleError(const ResourceError& error)
{
    // Copy the ResourceError instance to make it sure that the passed
    // ResourceError is alive during didFail() even when the Resource is
    // destructed during didFail().
    ResourceError copiedError = error;

    ThreadableLoaderClient* client = m_client;
    clear();
    client->didFail(copiedError);
    // |this| may be dead here.
}

void DocumentThreadableLoader::cancelWithError(const ResourceError& error)
{
    // Cancel can re-enter and m_resource might be null here as a result.
    if (!m_client || !resource()) {
        clear();
        return;
    }

    ResourceError errorForCallback = error;
    if (errorForCallback.isNull()) {
        // FIXME: This error is sent to the client in didFail(), so it should not be an internal one. Use FrameLoaderClient::cancelledError() instead.
        errorForCallback = ResourceError(errorDomainBlinkInternal, 0, resource()->url().string(), "Load cancelled");
        errorForCallback.setIsCancellation(true);
    }

    ThreadableLoaderClient* client = m_client;
    clear();
    client->didFail(errorForCallback);
    // |this| may be dead here in async mode.
}

DocumentThreadableLoader::DocumentThreadableLoader(Document& document, ThreadableLoaderClient* client, BlockingBehavior blockingBehavior, const ResourceRequest& request, const ThreadableLoaderOptions& options, const ResourceLoaderOptions& resourceLoaderOptions)
    : m_client(client)
    , m_document(&document)
    , m_options(options)
    , m_resourceLoaderOptions(resourceLoaderOptions)
    , m_forceDoNotAllowStoredCredentials(false)
    , m_securityOrigin(m_resourceLoaderOptions.securityOrigin)
    , m_sameOriginRequest(securityOrigin()->canRequestNoSuborigin(request.url()))
    , m_crossOriginNonSimpleRequest(false)
    , m_isUsingDataConsumerHandle(false)
    , m_async(blockingBehavior == LoadAsynchronously)
    , m_requestContext(request.requestContext())
    , m_timeoutTimer(this, &DocumentThreadableLoader::didTimeout)
    , m_requestStartedSeconds(0.0)
    , m_corsRedirectLimit(kMaxCORSRedirects)
    , m_redirectMode(request.fetchRedirectMode())
{
    ASSERT(client);
    // Setting an outgoing referer is only supported in the async code path.
    ASSERT(m_async || request.httpReferrer().isEmpty());

    if (!m_sameOriginRequest && m_options.crossOriginRequestPolicy == DenyCrossOriginRequests) {
        ThreadableLoaderClient* client = m_client;
        clear();
        client->didFail(ResourceError(errorDomainBlinkInternal, 0, request.url().string(), "Cross origin requests are not supported."));
        // |this| may be dead here.
        return;
    }

    m_requestStartedSeconds = monotonicallyIncreasingTime();

    // Save any CORS simple headers on the request here. If this request redirects cross-origin, we cancel the old request
    // create a new one, and copy these headers.
    const HTTPHeaderMap& headerMap = request.httpHeaderFields();
    for (const auto& header : headerMap) {
        if (FetchUtils::isSimpleHeader(header.key, header.value)) {
            m_simpleRequestHeaders.add(header.key, header.value);
        } else if (equalIgnoringCase(header.key, HTTPNames::Range) && m_options.crossOriginRequestPolicy == UseAccessControl && m_options.preflightPolicy == PreventPreflight) {
            // Allow an exception for the "range" header for when CORS callers request no preflight, this ensures cross-origin
            // redirects work correctly for crossOrigin enabled WebURLRequest::RequestContextVideo type requests.
            m_simpleRequestHeaders.add(header.key, header.value);
        }
    }

    // DocumentThreadableLoader is used by all javascript initiated fetch, so
    // we use this chance to record non-GET fetch script requests.
    // However, this is based on the following assumptions, so please be careful
    // when adding similar logic:
    // - ThreadableLoader is used as backend for all javascript initiated network
    //   fetches.
    //   - Note that ThreadableLoader is also used for non-network fetch such as
    //     FileReaderLoader. However it emulates GET method so signal is not
    //     recorded here.
    // - ThreadableLoader w/ non-GET request is only created from javascript
    //   initiated fetch.
    //   - Some non-script initiated fetches such as WorkerScriptLoader also use
    //     ThreadableLoader, but they are guaranteed to use GET method.
    if (request.httpMethod() != HTTPNames::GET) {
        if (Page* page = document.page())
            page->chromeClient().didObserveNonGetFetchFromScript();
    }

    // If the fetch request will be handled by the ServiceWorker, the
    // FetchRequestMode of the request must be FetchRequestModeCORS or
    // FetchRequestModeCORSWithForcedPreflight. Otherwise the ServiceWorker can
    // return a opaque response which is from the other origin site and the
    // script in the page can read the content.
    //
    // We assume that ServiceWorker is skipped for sync requests and unsupported
    // protocol requests by content/ code.
    if (m_async && !request.skipServiceWorker() && SchemeRegistry::shouldTreatURLSchemeAsAllowingServiceWorkers(request.url().protocol()) && document.fetcher()->isControlledByServiceWorker()) {
        ResourceRequest newRequest(request);
        // FetchRequestMode should be set by the caller. But the expected value
        // of FetchRequestMode is not speced yet except for XHR. So we set here.
        // FIXME: When we support fetch API in document, this value should not
        // be overridden here.
        if (options.preflightPolicy == ForcePreflight)
            newRequest.setFetchRequestMode(WebURLRequest::FetchRequestModeCORSWithForcedPreflight);
        else
            newRequest.setFetchRequestMode(WebURLRequest::FetchRequestModeCORS);

        m_fallbackRequestForServiceWorker = ResourceRequest(request);
        m_fallbackRequestForServiceWorker.setSkipServiceWorker(true);

        loadRequest(newRequest, m_resourceLoaderOptions);
        return;
    }

    dispatchInitialRequest(request);
    // |this| may be dead here in async mode.
}

void DocumentThreadableLoader::loadRequest(const ResourceRequest& request, ResourceLoaderOptions resourceLoaderOptions)
{
    // Any credential should have been removed from the cross-site requests.
    const KURL& requestURL = request.url();
    ASSERT(m_sameOriginRequest || requestURL.user().isEmpty());
    ASSERT(m_sameOriginRequest || requestURL.pass().isEmpty());

    // Update resourceLoaderOptions with enforced values.
    if (m_forceDoNotAllowStoredCredentials)
        resourceLoaderOptions.allowCredentials = DoNotAllowStoredCredentials;
    resourceLoaderOptions.securityOrigin = m_securityOrigin;
    if (m_async) {
        if (!m_actualRequest.isNull())
            resourceLoaderOptions.dataBufferingPolicy = BufferData;

        if (m_options.timeoutMilliseconds > 0)
            m_timeoutTimer.startOneShot(m_options.timeoutMilliseconds / 1000.0, BLINK_FROM_HERE);

        FetchRequest newRequest(request, m_options.initiator, resourceLoaderOptions);
        if (m_options.crossOriginRequestPolicy == AllowCrossOriginRequests)
            newRequest.setOriginRestriction(FetchRequest::NoOriginRestriction);
        ASSERT(!resource());

        WeakPtr<DocumentThreadableLoader> self(m_weakFactory.createWeakPtr());

        if (request.requestContext() == WebURLRequest::RequestContextVideo || request.requestContext() == WebURLRequest::RequestContextAudio)
            setResource(RawResource::fetchMedia(newRequest, document().fetcher()));
        else if (request.requestContext() == WebURLRequest::RequestContextManifest)
            setResource(RawResource::fetchManifest(newRequest, document().fetcher()));
        else
            setResource(RawResource::fetch(newRequest, document().fetcher()));

        // setResource() might call notifyFinished() synchronously, and thus
        // clear() might be called and |this| may be dead here.
        if (!self)
            return;

        if (!resource()) {
            InspectorInstrumentation::documentThreadableLoaderFailedToStartLoadingForClient(m_document, m_client);
            ThreadableLoaderClient* client = m_client;
            clear();
            // setResource() might call notifyFinished() and thus clear()
            // synchronously, and in such cases ThreadableLoaderClient is
            // already notified and |client| is null.
            if (!client)
                return;
            client->didFail(ResourceError(errorDomainBlinkInternal, 0, requestURL.getString(), "Failed to start loading."));
            // |this| may be dead here.
            return;
        }

        if (resource()->loader()) {
            unsigned long identifier = resource()->identifier();
            InspectorInstrumentation::documentThreadableLoaderStartedLoadingForClient(m_document, identifier, m_client);
        } else {
            InspectorInstrumentation::documentThreadableLoaderFailedToStartLoadingForClient(m_document, m_client);
        }
        return;
    }

    FetchRequest fetchRequest(request, m_options.initiator, resourceLoaderOptions);
    if (m_options.crossOriginRequestPolicy == AllowCrossOriginRequests)
        fetchRequest.setOriginRestriction(FetchRequest::NoOriginRestriction);
    Resource* resource = RawResource::fetchSynchronously(fetchRequest, document().fetcher());
    ResourceResponse response = resource ? resource->response() : ResourceResponse();
    unsigned long identifier = resource ? resource->identifier() : std::numeric_limits<unsigned long>::max();
    ResourceError error = resource ? resource->resourceError() : ResourceError();

    InspectorInstrumentation::documentThreadableLoaderStartedLoadingForClient(m_document, identifier, m_client);

    if (!resource) {
        m_client->didFail(error);
        return;
    }

    // No exception for file:/// resources, see <rdar://problem/4962298>.
    // Also, if we have an HTTP response, then it wasn't a network error in fact.
    if (!error.isNull() && !requestURL.isLocalFile() && response.httpStatusCode() <= 0) {
        m_client->didFail(error);
        return;
    }

    // FIXME: A synchronous request does not tell us whether a redirect happened or not, so we guess by comparing the
    // request and response URLs. This isn't a perfect test though, since a server can serve a redirect to the same URL that was
    // requested. Also comparing the request and response URLs as strings will fail if the requestURL still has its credentials.
    if (requestURL != response.url() && !isAllowedRedirect(response.url())) {
        m_client->didFailRedirectCheck();
        return;
    }

    handleResponse(identifier, response, nullptr);

    // handleResponse() may detect an error. In such a case (check |m_client|
    // as it gets reset by clear() call), skip the rest.
    //
    // |this| is alive here since loadResourceSynchronously() keeps it alive
    // until the end of the function.
    if (!m_client)
        return;

//.........这里部分代码省略.........