Revert of ServiceWorkerWriteToCacheJob: refactor

content/browser/service_worker/service_worker_write_to_cache_job.cc

Index: content/browser/service_worker/service_worker_write_to_cache_job.cc
diff --git a/content/browser/service_worker/service_worker_write_to_cache_job.cc b/content/browser/service_worker/service_worker_write_to_cache_job.cc
index c3ea949be39cfc3fd03215bc0dae57abeee37211..781a65257b61f1371eb8eaa703cdae73565c3dd0 100644
--- a/content/browser/service_worker/service_worker_write_to_cache_job.cc
+++ b/content/browser/service_worker/service_worker_write_to_cache_job.cc
@@ -4,11 +4,10 @@
 
 #include "content/browser/service_worker/service_worker_write_to_cache_job.h"
 
-#include "base/bind.h"
-#include "base/callback.h"
+#include <algorithm>
+
 #include "base/strings/stringprintf.h"
 #include "base/trace_event/trace_event.h"
-#include "content/browser/service_worker/service_worker_cache_writer.h"
 #include "content/browser/service_worker/service_worker_context_core.h"
 #include "content/browser/service_worker/service_worker_disk_cache.h"
 #include "content/browser/service_worker/service_worker_metrics.h"
@@ -19,6 +18,7 @@
 #include "net/http/http_network_session.h"
 #include "net/http/http_request_headers.h"
 #include "net/http/http_response_headers.h"
+#include "net/http/http_util.h"
 #include "net/url_request/url_request.h"
 #include "net/url_request/url_request_context.h"
 #include "net/url_request/url_request_status.h"
@@ -40,7 +40,259 @@
     "The script resource is behind a redirect, which is disallowed.";
 const char kServiceWorkerAllowed[] = "Service-Worker-Allowed";
 
+const int kBufferSize = 16 * 1024;
+
 }  // namespace
+
+// Reads an existing resource and copies it via
+// ServiceWorkerWriteToCacheJob::WriteData.
+class ServiceWorkerWriteToCacheJob::Copier : public base::RefCounted<Copier> {
+ public:
+  Copier(base::WeakPtr<ServiceWorkerWriteToCacheJob> owner,
+         scoped_ptr<ServiceWorkerResponseReader> reader,
+         int bytes_to_copy,
+         const base::Callback<void(ServiceWorkerStatusCode)>& callback)
+      : owner_(owner),
+        reader_(reader.release()),
+        bytes_to_copy_(bytes_to_copy),
+        callback_(callback) {
+    DCHECK_LT(0, bytes_to_copy_);
+  }
+
+  void Start() {
+    io_buffer_ = new net::IOBuffer(kBufferSize);
+    ReadSomeData();
+  }
+
+ private:
+  friend class base::RefCounted<Copier>;
+  ~Copier() {}
+
+  void ReadSomeData() {
+    reader_->ReadData(io_buffer_.get(), kBufferSize,
+                      base::Bind(&Copier::OnReadDataComplete, this));
+  }
+
+  void OnReadDataComplete(int result) {
+    if (!owner_)
+      return;
+    if (result <= 0) {
+      // We hit EOF or error but weren't done copying.
+      Complete(SERVICE_WORKER_ERROR_FAILED);
+      return;
+    }
+
+    int bytes_to_write = std::min(bytes_to_copy_, result);
+    owner_->WriteData(io_buffer_.get(), bytes_to_write,
+                      base::Bind(&Copier::OnWriteDataComplete, this));
+  }
+
+  void OnWriteDataComplete(int result) {
+    if (result < 0) {
+      Complete(SERVICE_WORKER_ERROR_FAILED);
+      return;
+    }
+
+    DCHECK_LE(result, bytes_to_copy_);
+    bytes_to_copy_ -= result;
+    if (bytes_to_copy_ == 0) {
+      Complete(SERVICE_WORKER_OK);
+      return;
+    }
+
+    ReadSomeData();
+  }
+
+  void Complete(ServiceWorkerStatusCode status) {
+    if (!owner_)
+      return;
+    callback_.Run(status);
+  }
+
+  base::WeakPtr<ServiceWorkerWriteToCacheJob> owner_;
+  scoped_ptr<ServiceWorkerResponseReader> reader_;
+  int bytes_to_copy_ = 0;
+  base::Callback<void(ServiceWorkerStatusCode)> callback_;
+  scoped_refptr<net::IOBuffer> io_buffer_;
+};
+
+// Abstract consumer for ServiceWorkerWriteToCacheJob that processes data from
+// the network.
+class ServiceWorkerWriteToCacheJob::NetDataConsumer {
+ public:
+  virtual ~NetDataConsumer() {}
+
+  // Called by |owner_|'s OnResponseStarted.
+  virtual void OnResponseStarted() = 0;
+
+  // HandleData should call |owner_|->NotifyReadComplete() when done.
+  virtual void HandleData(net::IOBuffer* buf, int size) = 0;
+};
+
+// Dumb consumer that just writes everything it sees to disk.
+class ServiceWorkerWriteToCacheJob::PassThroughConsumer
+    : public ServiceWorkerWriteToCacheJob::NetDataConsumer {
+ public:
+  explicit PassThroughConsumer(ServiceWorkerWriteToCacheJob* owner)
+      : owner_(owner), weak_factory_(this) {}
+  ~PassThroughConsumer() override {}
+
+  void OnResponseStarted() override {
+    owner_->WriteHeaders(
+        base::Bind(&PassThroughConsumer::OnWriteHeadersComplete,
+                   weak_factory_.GetWeakPtr()));
+    owner_->SetPendingIO();
+  }
+
+  void HandleData(net::IOBuffer* buf, int size) override {
+    if (size == 0) {
+      owner_->OnPassThroughComplete();
+      return;
+    }
+
+    owner_->WriteData(buf, size,
+                      base::Bind(&PassThroughConsumer::OnWriteDataComplete,
+                                 weak_factory_.GetWeakPtr()));
+    owner_->SetPendingIO();
+  }
+
+ private:
+  void OnWriteHeadersComplete() {
+    owner_->ClearPendingIO();
+    owner_->CommitHeadersAndNotifyHeadersComplete();
+  }
+
+  void OnWriteDataComplete(int result) {
+    owner_->ClearPendingIO();
+    owner_->NotifyReadComplete(result);
+  }
+
+  ServiceWorkerWriteToCacheJob* owner_;
+  base::WeakPtrFactory<PassThroughConsumer> weak_factory_;
+};
+
+// Compares an existing resource with data progressively fed to it.
+// Calls back to |owner|->OnCompareComplete once done.
+class ServiceWorkerWriteToCacheJob::Comparer
+    : public ServiceWorkerWriteToCacheJob::NetDataConsumer {
+ public:
+  Comparer(ServiceWorkerWriteToCacheJob* owner,
+           scoped_ptr<ServiceWorkerResponseReader> reader)
+      : owner_(owner), reader_(reader.release()), weak_factory_(this) {}
+  ~Comparer() override {}
+
+  void OnResponseStarted() override {
+    owner_->CommitHeadersAndNotifyHeadersComplete();
+  }
+
+  void HandleData(net::IOBuffer* buf, int size) override {
+    net_data_ = buf;
+    net_data_offset_ = 0;
+    net_data_size_ = size;
+
+    if (size == 0 && info_) {
+      Complete(bytes_matched_ == info_->response_data_size);
+      return;
+    }
+
+    if (!info_) {
+      read_buffer_ = new net::IOBuffer(kBufferSize);
+      info_ = new HttpResponseInfoIOBuffer;
+      reader_->ReadInfo(info_.get(), base::Bind(&Comparer::OnReadInfoComplete,
+                                                weak_factory_.GetWeakPtr()));
+      owner_->SetPendingIO();
+      return;
+    }
+
+    ReadSomeData();
+    owner_->SetPendingIO();
+  }
+
+ private:
+  int bytes_remaining() {
+    DCHECK(net_data_);
+    DCHECK_LE(0, net_data_offset_);
+    DCHECK_LE(net_data_offset_, net_data_size_);
+    return net_data_size_ - net_data_offset_;
+  }
+
+  void OnReadInfoComplete(int result) {
+    if (result < 0) {
+      Complete(false);
+      return;
+    }
+
+    if (bytes_remaining() == 0) {
+      Complete(bytes_matched_ == info_->response_data_size);
+      return;
+    }
+
+    ReadSomeData();
+  }
+
+  void ReadSomeData() {
+    DCHECK_LT(0, bytes_remaining());
+    int bytes_to_read = std::min(bytes_remaining(), kBufferSize);
+    reader_->ReadData(
+        read_buffer_.get(), bytes_to_read,
+        base::Bind(&Comparer::OnReadDataComplete, weak_factory_.GetWeakPtr()));
+  }
+
+  void OnReadDataComplete(int result) {
+    if (result <= 0) {
+      // We hit error or EOF but had more to compare.
+      Complete(false);
+      return;
+    }
+
+    DCHECK_LE(result, bytes_remaining());
+    if (memcmp(net_data_->data() + net_data_offset_, read_buffer_->data(),
+               result) != 0) {
+      Complete(false);
+      return;
+    }
+
+    net_data_offset_ += result;
+    if (bytes_remaining() == 0) {
+      NotifyReadComplete();
+      return;
+    }
+
+    ReadSomeData();
+  }
+
+  // Completes one HandleData() call.
+  void NotifyReadComplete() {
+    int size = net_data_size_;
+    net_data_ = nullptr;
+    net_data_offset_ = 0;
+    net_data_size_ = 0;
+
+    bytes_matched_ += size;
+    owner_->ClearPendingIO();
+    owner_->NotifyReadComplete(size);
+  }
+
+  // Completes the entire Comparer.
+  void Complete(bool is_equal) {
+    owner_->OnCompareComplete(bytes_matched_, is_equal);
+  }
+
+  ServiceWorkerWriteToCacheJob* owner_;
+  scoped_ptr<ServiceWorkerResponseReader> reader_;
+  scoped_refptr<net::IOBuffer> read_buffer_;
+  scoped_refptr<HttpResponseInfoIOBuffer> info_;
+
+  // Cumulative number of bytes successfully compared.
+  int bytes_matched_ = 0;
+
+  // State used for one HandleData() call.
+  scoped_refptr<net::IOBuffer> net_data_;
+  int net_data_offset_ = 0;
+  int net_data_size_ = 0;
+
+  base::WeakPtrFactory<Comparer> weak_factory_;
+};
 
 ServiceWorkerWriteToCacheJob::ServiceWorkerWriteToCacheJob(
     net::URLRequest* request,
@@ -79,14 +331,14 @@
         net::URLRequestStatus::FAILED, net::ERR_FAILED));
     return;
   }
-
-  // These uses of Unretained are safe because this object is the sole owner of
-  // |cache_writer_|, which in turn is the sole user of these callbacks.
-  cache_writer_.reset(new ServiceWorkerCacheWriter(
-      base::Bind(&ServiceWorkerWriteToCacheJob::CreateCacheResponseReader,
-                 base::Unretained(this)),
-      base::Bind(&ServiceWorkerWriteToCacheJob::CreateCacheResponseWriter,
-                 base::Unretained(this))));
+  if (incumbent_response_id_ != kInvalidServiceWorkerResourceId) {
+    scoped_ptr<ServiceWorkerResponseReader> incumbent_reader =
+        context_->storage()->CreateResponseReader(incumbent_response_id_);
+    consumer_.reset(new Comparer(this, incumbent_reader.Pass()));
+  } else {
+    consumer_.reset(new PassThroughConsumer(this));
+  }
+
   version_->script_cache_map()->NotifyStartedCaching(
       url_, response_id_);
   did_notify_started_ = true;
@@ -99,9 +351,12 @@
   weak_factory_.InvalidateWeakPtrs();
   has_been_killed_ = true;
   net_request_.reset();
-  if (did_notify_started_) {
-    NotifyFinishedCaching(net::URLRequestStatus::FromError(net::ERR_ABORTED),
-                          kKilledError);
+  if (did_notify_started_ && !did_notify_finished_) {
+    version_->script_cache_map()->NotifyFinishedCaching(
+        url_, -1,
+        net::URLRequestStatus(net::URLRequestStatus::FAILED, net::ERR_ABORTED),
+        kKilledError);
+    did_notify_finished_ = true;
   }
   writer_.reset();
   context_.reset();
@@ -157,15 +412,17 @@
     return false;
 
   if (!status.is_success()) {
-    NotifyDoneHelper(status, kFetchScriptError);
+    AsyncNotifyDoneHelper(status, kFetchScriptError);
     return false;
   }
 
-  HandleNetData(*bytes_read);
-  // Since URLRequestStatus::is_success() means "SUCCESS or IO_PENDING", but the
-  // contract of this function is "return true for synchronous successes only",
-  // it is important to test against SUCCESS explicitly here.
-  return GetStatus().status() == net::URLRequestStatus::SUCCESS;
+  DCHECK_EQ(0, *bytes_read);
+  consumer_->HandleData(buf, 0);
+  if (did_notify_finished_)
+    return GetStatus().is_success();
+  if (GetStatus().is_io_pending())
+    return false;
+  return status.is_success();
 }
 
 const net::HttpResponseInfo* ServiceWorkerWriteToCacheJob::http_info() const {
@@ -204,12 +461,102 @@
     int* bytes_read) {
   DCHECK_GT(buf_size, 0);
   DCHECK(bytes_read);
+  *bytes_read = 0;
   io_buffer_ = buf;
   io_buffer_bytes_ = 0;
-  if (!net_request_->Read(buf, buf_size, bytes_read))
-    DCHECK_NE(net::URLRequestStatus::SUCCESS, net_request_->status().status());
-
+  int net_bytes_read = 0;
+  if (!net_request_->Read(buf, buf_size, &net_bytes_read)) {
+    if (net_request_->status().is_io_pending())
+      return net_request_->status();
+    DCHECK(!net_request_->status().is_success());
+    return net_request_->status();
+  }
+
+  if (net_bytes_read != 0) {
+    HandleNetData(net_bytes_read);
+    DCHECK(GetStatus().is_io_pending());
+    return GetStatus();
+  }
+
+  DCHECK(net_request_->status().is_success());
   return net_request_->status();
+}
+
+void ServiceWorkerWriteToCacheJob::WriteHeaders(const base::Closure& callback) {
+  if (!context_) {
+    AsyncNotifyDoneHelper(
+        net::URLRequestStatus(net::URLRequestStatus::FAILED, net::ERR_FAILED),
+        kFetchScriptError);
+    return;
+  }
+  TRACE_EVENT_ASYNC_STEP_INTO0("ServiceWorker",
+                               "ServiceWorkerWriteToCacheJob::ExecutingJob",
+                               this, "WriteHeaders");
+  writer_ = context_->storage()->CreateResponseWriter(response_id_);
+  scoped_refptr<HttpResponseInfoIOBuffer> info_buffer =
+      new HttpResponseInfoIOBuffer(
+          new net::HttpResponseInfo(net_request_->response_info()));
+  writer_->WriteInfo(
+      info_buffer.get(),
+      base::Bind(&ServiceWorkerWriteToCacheJob::OnWriteHeadersComplete,
+                 weak_factory_.GetWeakPtr(), callback));
+}
+
+void ServiceWorkerWriteToCacheJob::OnWriteHeadersComplete(
+    const base::Closure& callback,
+    int result) {
+  if (result < 0) {
+    ServiceWorkerMetrics::CountWriteResponseResult(
+        ServiceWorkerMetrics::WRITE_HEADERS_ERROR);
+    AsyncNotifyDoneHelper(
+        net::URLRequestStatus(net::URLRequestStatus::FAILED, result),
+        kFetchScriptError);
+    return;
+  }
+  TRACE_EVENT_ASYNC_STEP_INTO0("ServiceWorker",
+                               "ServiceWorkerWriteToCacheJob::ExecutingJob",
+                               this, "WriteHeadersCompleted");
+  callback.Run();
+}
+
+void ServiceWorkerWriteToCacheJob::WriteData(
+    net::IOBuffer* buf,
+    int bytes_to_write,
+    const base::Callback<void(int result)>& callback) {
+  DCHECK_LT(0, bytes_to_write);
+  TRACE_EVENT_ASYNC_STEP_INTO1(
+      "ServiceWorker", "ServiceWorkerWriteToCacheJob::ExecutingJob", this,
+      "WriteData", "Amount to write", bytes_to_write);
+
+  writer_->WriteData(
+      buf, bytes_to_write,
+      base::Bind(&ServiceWorkerWriteToCacheJob::OnWriteDataComplete,
+                 weak_factory_.GetWeakPtr(), callback));
+}
+
+void ServiceWorkerWriteToCacheJob::OnWriteDataComplete(
+    const base::Callback<void(int result)>& callback,
+    int result) {
+  DCHECK_NE(0, result);
+  if (!context_) {
+    AsyncNotifyDoneHelper(
+        net::URLRequestStatus(net::URLRequestStatus::FAILED, net::ERR_FAILED),
+        kFetchScriptError);
+    return;
+  }
+  if (result < 0) {
+    ServiceWorkerMetrics::CountWriteResponseResult(
+        ServiceWorkerMetrics::WRITE_DATA_ERROR);
+    AsyncNotifyDoneHelper(
+        net::URLRequestStatus(net::URLRequestStatus::FAILED, result),
+        kFetchScriptError);
+    return;
+  }
+  ServiceWorkerMetrics::CountWriteResponseResult(
+      ServiceWorkerMetrics::WRITE_OK);
+  callback.Run(result);
+  TRACE_EVENT_ASYNC_END0("ServiceWorker",
+                         "ServiceWorkerWriteToCacheJob::ExecutingJob", this);
 }
 
 void ServiceWorkerWriteToCacheJob::OnReceivedRedirect(
@@ -220,9 +567,9 @@
   TRACE_EVENT0("ServiceWorker",
                "ServiceWorkerWriteToCacheJob::OnReceivedRedirect");
   // Script resources can't redirect.
-  NotifyDoneHelper(net::URLRequestStatus(net::URLRequestStatus::FAILED,
-                                         net::ERR_UNSAFE_REDIRECT),
-                   kRedirectError);
+  AsyncNotifyDoneHelper(net::URLRequestStatus(net::URLRequestStatus::FAILED,
+                                              net::ERR_UNSAFE_REDIRECT),
+                        kRedirectError);
 }
 
 void ServiceWorkerWriteToCacheJob::OnAuthRequired(
@@ -232,7 +579,7 @@
   TRACE_EVENT0("ServiceWorker",
                "ServiceWorkerWriteToCacheJob::OnAuthRequired");
   // TODO(michaeln): Pass this thru to our jobs client.
-  NotifyDoneHelper(
+  AsyncNotifyDoneHelper(
       net::URLRequestStatus(net::URLRequestStatus::FAILED, net::ERR_FAILED),
       kClientAuthenticationError);
 }
@@ -245,7 +592,7 @@
                "ServiceWorkerWriteToCacheJob::OnCertificateRequested");
   // TODO(michaeln): Pass this thru to our jobs client.
   // see NotifyCertificateRequested.
-  NotifyDoneHelper(
+  AsyncNotifyDoneHelper(
       net::URLRequestStatus(net::URLRequestStatus::FAILED, net::ERR_FAILED),
       kClientAuthenticationError);
 }
@@ -259,9 +606,9 @@
                "ServiceWorkerWriteToCacheJob::OnSSLCertificateError");
   // TODO(michaeln): Pass this thru to our jobs client,
   // see NotifySSLCertificateError.
-  NotifyDoneHelper(net::URLRequestStatus(net::URLRequestStatus::FAILED,
-                                         net::ERR_INSECURE_RESPONSE),
-                   kSSLError);
+  AsyncNotifyDoneHelper(net::URLRequestStatus(net::URLRequestStatus::FAILED,
+                                              net::ERR_INSECURE_RESPONSE),
+                        kSSLError);
 }
 
 void ServiceWorkerWriteToCacheJob::OnBeforeNetworkStart(
@@ -277,15 +624,15 @@
     net::URLRequest* request) {
   DCHECK_EQ(net_request_, request);
   if (!request->status().is_success()) {
-    NotifyDoneHelper(request->status(), kFetchScriptError);
+    AsyncNotifyDoneHelper(request->status(), kFetchScriptError);
     return;
   }
   if (request->GetResponseCode() / 100 != 2) {
     std::string error_message =
         base::StringPrintf(kBadHTTPResponseError, request->GetResponseCode());
-    NotifyDoneHelper(net::URLRequestStatus(net::URLRequestStatus::FAILED,
-                                           net::ERR_INVALID_RESPONSE),
-                     error_message);
+    AsyncNotifyDoneHelper(net::URLRequestStatus(net::URLRequestStatus::FAILED,
+                                                net::ERR_INVALID_RESPONSE),
+                          error_message);
     // TODO(michaeln): Instead of error'ing immediately, send the net
     // response to our consumer, just don't cache it?
     return;
@@ -296,9 +643,9 @@
     const net::HttpNetworkSession::Params* session_params =
         request->context()->GetNetworkSessionParams();
     if (!session_params || !session_params->ignore_certificate_errors) {
-      NotifyDoneHelper(net::URLRequestStatus(net::URLRequestStatus::FAILED,
-                                             net::ERR_INSECURE_RESPONSE),
-                       kSSLError);
+      AsyncNotifyDoneHelper(net::URLRequestStatus(net::URLRequestStatus::FAILED,
+                                                  net::ERR_INSECURE_RESPONSE),
+                            kSSLError);
       return;
     }
   }
@@ -313,9 +660,9 @@
           mime_type.empty()
               ? kNoMIMEError
               : base::StringPrintf(kBadMIMEError, mime_type.c_str());
-      NotifyDoneHelper(net::URLRequestStatus(net::URLRequestStatus::FAILED,
-                                             net::ERR_INSECURE_RESPONSE),
-                       error_message);
+      AsyncNotifyDoneHelper(net::URLRequestStatus(net::URLRequestStatus::FAILED,
+                                                  net::ERR_INSECURE_RESPONSE),
+                            error_message);
       return;
     }
 
@@ -328,47 +675,17 @@
   if (net_request_->response_info().network_accessed)
     version_->embedded_worker()->OnNetworkAccessedForScriptLoad();
 
+  consumer_->OnResponseStarted();
+}
+
+void ServiceWorkerWriteToCacheJob::CommitHeadersAndNotifyHeadersComplete() {
   http_info_.reset(new net::HttpResponseInfo(net_request_->response_info()));
-  scoped_refptr<HttpResponseInfoIOBuffer> info_buffer =
-      new HttpResponseInfoIOBuffer(
-          new net::HttpResponseInfo(net_request_->response_info()));
-  net::Error error = cache_writer_->MaybeWriteHeaders(
-      info_buffer.get(),
-      base::Bind(&ServiceWorkerWriteToCacheJob::OnWriteHeadersComplete,
-                 weak_factory_.GetWeakPtr()));
-  SetStatus(net::URLRequestStatus::FromError(error));
-  if (error != net::ERR_IO_PENDING)
-    NotifyHeadersComplete();
-}
-
-void ServiceWorkerWriteToCacheJob::OnWriteHeadersComplete(net::Error error) {
-  SetStatus(net::URLRequestStatus::FromError(error));
   NotifyHeadersComplete();
 }
 
 void ServiceWorkerWriteToCacheJob::HandleNetData(int bytes_read) {
   io_buffer_bytes_ = bytes_read;
-  net::Error error = cache_writer_->MaybeWriteData(
-      io_buffer_.get(), bytes_read,
-      base::Bind(&ServiceWorkerWriteToCacheJob::OnWriteDataComplete,
-                 weak_factory_.GetWeakPtr()));
-  SetStatus(net::URLRequestStatus::FromError(error));
-
-  // In case of ERR_IO_PENDING, this logic is done in OnWriteDataComplete.
-  if (error != net::ERR_IO_PENDING && bytes_read == 0) {
-    NotifyFinishedCaching(net::URLRequestStatus::FromError(error),
-                          std::string());
-  }
-}
-
-void ServiceWorkerWriteToCacheJob::OnWriteDataComplete(net::Error error) {
-  SetStatus(net::URLRequestStatus::FromError(error));
-  DCHECK_NE(net::ERR_IO_PENDING, error);
-  if (io_buffer_bytes_ == 0) {
-    NotifyFinishedCaching(net::URLRequestStatus::FromError(error),
-                          std::string());
-  }
-  NotifyReadComplete(error == net::OK ? io_buffer_bytes_ : error);
+  consumer_->HandleData(io_buffer_.get(), bytes_read);
 }
 
 void ServiceWorkerWriteToCacheJob::OnReadCompleted(
@@ -377,10 +694,18 @@
   DCHECK_EQ(net_request_, request);
   if (bytes_read < 0) {
     DCHECK(!request->status().is_success());
-    NotifyDoneHelper(request->status(), kFetchScriptError);
-    return;
-  }
-  HandleNetData(bytes_read);
+    AsyncNotifyDoneHelper(request->status(), kFetchScriptError);
+    return;
+  }
+  if (bytes_read > 0) {
+    HandleNetData(bytes_read);
+    DCHECK(GetStatus().is_io_pending());
+    return;
+  }
+
+  // No more data to process, the job is complete.
+  DCHECK(request->status().is_success());
+  HandleNetData(0);
 }
 
 bool ServiceWorkerWriteToCacheJob::CheckPathRestriction(
@@ -394,15 +719,89 @@
   if (!ServiceWorkerUtils::IsPathRestrictionSatisfied(
           version_->scope(), url_,
           has_header ? &service_worker_allowed : nullptr, &error_message)) {
-    NotifyDoneHelper(net::URLRequestStatus(net::URLRequestStatus::FAILED,
-                                           net::ERR_INSECURE_RESPONSE),
-                     error_message);
+    AsyncNotifyDoneHelper(net::URLRequestStatus(net::URLRequestStatus::FAILED,
+                                                net::ERR_INSECURE_RESPONSE),
+                          error_message);
     return false;
   }
   return true;
 }
 
-void ServiceWorkerWriteToCacheJob::NotifyDoneHelper(
+void ServiceWorkerWriteToCacheJob::SetPendingIO() {
+  SetStatus(net::URLRequestStatus(net::URLRequestStatus::IO_PENDING, 0));
+}
+
+void ServiceWorkerWriteToCacheJob::ClearPendingIO() {
+  SetStatus(net::URLRequestStatus());
+}
+
+void ServiceWorkerWriteToCacheJob::OnPassThroughComplete() {
+  NotifyFinishedCaching(net::URLRequestStatus(), std::string());
+  if (GetStatus().is_io_pending()) {
+    ClearPendingIO();
+    NotifyReadComplete(0);
+  }
+}
+
+void ServiceWorkerWriteToCacheJob::OnCompareComplete(int bytes_matched,
+                                                     bool is_equal) {
+  if (is_equal) {
+    // This version is identical to the incumbent, so discard it and fail this
+    // job.
+    version_->SetStartWorkerStatusCode(SERVICE_WORKER_ERROR_EXISTS);
+    AsyncNotifyDoneHelper(
+        net::URLRequestStatus(net::URLRequestStatus::FAILED, net::ERR_FAILED),
+        kFetchScriptError);
+    return;
+  }
+
+  // We must switch to the pass through consumer. Write what is known
+  // (headers + bytes matched) to disk.
+  WriteHeaders(base::Bind(&ServiceWorkerWriteToCacheJob::CopyIncumbent,
+                          weak_factory_.GetWeakPtr(), bytes_matched));
+  SetPendingIO();
+}
+
+void ServiceWorkerWriteToCacheJob::CopyIncumbent(int bytes_to_copy) {
+  if (bytes_to_copy == 0) {
+    OnCopyComplete(SERVICE_WORKER_OK);
+    return;
+  }
+  scoped_ptr<ServiceWorkerResponseReader> incumbent_reader =
+      context_->storage()->CreateResponseReader(incumbent_response_id_);
+  scoped_refptr<Copier> copier = new Copier(
+      weak_factory_.GetWeakPtr(), incumbent_reader.Pass(), bytes_to_copy,
+      base::Bind(&ServiceWorkerWriteToCacheJob::OnCopyComplete,
+                 weak_factory_.GetWeakPtr()));
+  copier->Start();  // It deletes itself when done.
+  DCHECK(GetStatus().is_io_pending());
+}
+
+void ServiceWorkerWriteToCacheJob::OnCopyComplete(
+    ServiceWorkerStatusCode status) {
+  if (status != SERVICE_WORKER_OK) {
+    AsyncNotifyDoneHelper(
+        net::URLRequestStatus(net::URLRequestStatus::FAILED, net::ERR_FAILED),
+        kFetchScriptError);
+    return;
+  }
+
+  // Continue processing the net data that triggered the comparison fail and
+  // copy.
+  if (io_buffer_bytes_ > 0) {
+    consumer_.reset(new PassThroughConsumer(this));
+    consumer_->HandleData(io_buffer_.get(), io_buffer_bytes_);
+    return;
+  }
+
+  // The copy was triggered by EOF from the network, which
+  // means the job is now done.
+  NotifyFinishedCaching(net::URLRequestStatus(), std::string());
+  ClearPendingIO();
+  NotifyReadComplete(0);
+}
+
+void ServiceWorkerWriteToCacheJob::AsyncNotifyDoneHelper(
     const net::URLRequestStatus& status,
     const std::string& status_message) {
   DCHECK(!status.is_io_pending());
@@ -414,39 +813,13 @@
 void ServiceWorkerWriteToCacheJob::NotifyFinishedCaching(
     net::URLRequestStatus status,
     const std::string& status_message) {
-  if (did_notify_finished_)
-    return;
-
-  // If all the calls to MaybeWriteHeaders/MaybeWriteData succeeded, but the
-  // incumbent entry wasn't actually replaced because the new entry was
-  // equivalent, the new version didn't actually install because it already
-  // exists.
-  if (status.status() == net::URLRequestStatus::SUCCESS &&
-      !cache_writer_->did_replace()) {
-    status =
-        net::URLRequestStatus(net::URLRequestStatus::FAILED, net::ERR_FAILED);
-    version_->SetStartWorkerStatusCode(SERVICE_WORKER_ERROR_EXISTS);
-  }
-
+  DCHECK(!did_notify_finished_);
   int size = -1;
   if (status.is_success())
-    size = cache_writer_->bytes_written();
-
+    size = writer_ ? writer_->amount_written() : 0;
   version_->script_cache_map()->NotifyFinishedCaching(url_, size, status,
                                                       status_message);
   did_notify_finished_ = true;
 }
 
-scoped_ptr<ServiceWorkerResponseReader>
-ServiceWorkerWriteToCacheJob::CreateCacheResponseReader() {
-  if (incumbent_response_id_ != kInvalidServiceWorkerResponseId)
-    return context_->storage()->CreateResponseReader(incumbent_response_id_);
-  return nullptr;
-}
-
-scoped_ptr<ServiceWorkerResponseWriter>
-ServiceWorkerWriteToCacheJob::CreateCacheResponseWriter() {
-  return context_->storage()->CreateResponseWriter(response_id_);
-}
-
 }  // namespace content