Initial implementation of ServiceWorkerCache.

content/browser/service_worker/service_worker_cache.cc

Index: content/browser/service_worker/service_worker_cache.cc
diff --git a/content/browser/service_worker/service_worker_cache.cc b/content/browser/service_worker/service_worker_cache.cc
index d5028f00854f1f2d1241105442ee5f1ec94bb289..c9d5c1f04c79d224f5c895aa99f73844232b502a 100644
--- a/content/browser/service_worker/service_worker_cache.cc
+++ b/content/browser/service_worker/service_worker_cache.cc
@@ -7,11 +7,149 @@
 #include <string>
 
 #include "base/files/file_path.h"
+#include "base/guid.h"
+#include "base/message_loop/message_loop_proxy.h"
+#include "content/browser/fileapi/chrome_blob_storage_context.h"
+#include "content/browser/service_worker/service_worker_cache.pb.h"
+#include "content/public/browser/browser_thread.h"
+#include "net/base/io_buffer.h"
+#include "net/base/net_errors.h"
+#include "net/disk_cache/disk_cache.h"
 #include "net/url_request/url_request_context.h"
+#include "webkit/browser/blob/blob_data_handle.h"
 #include "webkit/browser/blob/blob_storage_context.h"
+#include "webkit/browser/blob/blob_url_request_job_factory.h"
 
 namespace content {
 
+namespace {
+// The maximum size of an individual cache.
+const int kMaxCacheBytes = 5 * 1024 * 1024;

[michaeln, 2014/08/14 10:35:20]

why so small?

[jkarlin, 2014/08/14 19:53:32]

Great question.  No idea what's proper.  Upped to 50MB for now.

+
+// Buffer size for cache and blob reading/writing.
+const int kBufferSize = 1024 * 512;

[michaeln, 2014/08/14 10:35:19]

why so big :)

[jkarlin, 2014/08/14 19:53:33]

This is the size that we read from the cache when streaming down to Blink for
normal loads.  See async_resource_handler.cc:38

+}
+
+struct ServiceWorkerCache::ResponseReadContext {
+  explicit ResponseReadContext(scoped_refptr<net::IOBufferWithSize> buff,

[michaeln, 2014/08/14 10:35:20]

is explicit needed with two args

[jkarlin, 2014/08/14 19:53:32]

Done.

+                               scoped_refptr<webkit_blob::BlobData> blob)
+      : buffer(buff), blob_data(blob), total_bytes_read(0) {}
+
+  scoped_refptr<net::IOBufferWithSize> buffer;
+  scoped_refptr<webkit_blob::BlobData> blob_data;
+  int total_bytes_read;
+
+  DISALLOW_COPY_AND_ASSIGN(ResponseReadContext);
+};
+
+// Streams data from a blob and writes it to a given disk_cache::Entry.
+// This class is owned by the callback function passed to Start().
+class ServiceWorkerCache::BlobReader : public net::URLRequest::Delegate {

[michaeln, 2014/08/14 10:35:20]

this is very similar to what ServiceWorkerWriteToCacheJob does, it reads a
network URLRequest and writes it to a net::DiskCache

[jkarlin, 2014/08/14 19:53:33]

True, but not a straight-forward adaptation.

+ public:
+  BlobReader(disk_cache::Entry* entry)
+      : cache_entry_offset_(0),
+        entry_(entry),
+        buffer_(new net::IOBufferWithSize(kBufferSize)) {
+    DCHECK(entry_);
+  }
+
+  void StreamBlobToCache(
+      net::URLRequestContext* request_context,
+      scoped_ptr<webkit_blob::BlobDataHandle> blob_data_handle,
+      const BoolCallback& callback) {
+    callback_ = callback;
+    blob_request_ = webkit_blob::BlobProtocolHandler::CreateBlobRequest(
+        blob_data_handle.Pass(), request_context, this);
+    blob_request_->Start();
+  }
+
+  // net::URLRequest::Delegate overrides for reading blobs.
+  virtual void OnReceivedRedirect(net::URLRequest* request,
+                                  const GURL& new_url,
+                                  bool* defer_redirect) OVERRIDE {
+    NOTREACHED();
+  }
+  virtual void OnAuthRequired(net::URLRequest* request,
+                              net::AuthChallengeInfo* auth_info) OVERRIDE {
+    NOTREACHED();
+  }
+  virtual void OnCertificateRequested(
+      net::URLRequest* request,
+      net::SSLCertRequestInfo* cert_request_info) OVERRIDE {
+    NOTREACHED();
+  }
+  virtual void OnSSLCertificateError(net::URLRequest* request,
+                                     const net::SSLInfo& ssl_info,
+                                     bool fatal) OVERRIDE {
+    NOTREACHED();
+  }
+  virtual void OnBeforeNetworkStart(net::URLRequest* request,
+                                    bool* defer) OVERRIDE {
+    NOTREACHED();
+  }
+
+  virtual void OnResponseStarted(net::URLRequest* request) OVERRIDE {
+    if (!request->status().is_success()) {
+      callback_.Run(false);
+      return;
+    }
+    ReadFromBlob();
+  }
+
+  virtual void ReadFromBlob() {
+    int bytes_read;
+    bool done =
+        blob_request_->Read(buffer_.get(), buffer_->size(), &bytes_read);
+    if (done)
+      OnReadCompleted(blob_request_.get(), bytes_read);
+  }
+
+  virtual void OnReadCompleted(net::URLRequest* request,
+                               int bytes_read) OVERRIDE {
+    if (!request->status().is_success()) {
+      callback_.Run(false);
+      return;
+    }
+
+    if (bytes_read == 0) {
+      callback_.Run(true);  // what should we really return here?
+      return;
+    }
+
+    net::CompletionCallback cache_write_callback = base::Bind(
+        &BlobReader::DidWriteDataToEntry, base::Unretained(this), bytes_read);
+
+    LOG(ERROR) << "Writing: " << std::string(buffer_->data(), bytes_read);
+
+    int rv = entry_->WriteData(ServiceWorkerCache::INDEX_RESPONSE_BODY,
+                               cache_entry_offset_,
+                               buffer_,
+                               bytes_read,
+                               cache_write_callback,
+                               false /* truncate */);  // what should this be?
+    if (rv != net::ERR_IO_PENDING) {
+      DidWriteDataToEntry(bytes_read, rv);
+    }
+  }
+
+  void DidWriteDataToEntry(int expected_bytes, int rv) {
+    if (rv != expected_bytes) {
+      callback_.Run(false);
+      return;
+    }
+
+    cache_entry_offset_ += rv;
+    ReadFromBlob();
+  }
+
+ private:
+  int cache_entry_offset_;
+  disk_cache::Entry* entry_;
+  scoped_ptr<net::URLRequest> blob_request_;
+  BoolCallback callback_;
+  scoped_refptr<net::IOBufferWithSize> buffer_;
+};
+
 // static
 scoped_ptr<ServiceWorkerCache> ServiceWorkerCache::CreateMemoryCache(
     const std::string& name,
@@ -31,15 +169,412 @@ scoped_ptr<ServiceWorkerCache> ServiceWorkerCache::CreatePersistentCache(
       new ServiceWorkerCache(path, name, request_context, blob_context));
 }
 
-void ServiceWorkerCache::CreateBackend(
-    const base::Callback<void(bool)>& callback) {
-  callback.Run(true);
+ServiceWorkerCache::~ServiceWorkerCache() {
 }
 
 base::WeakPtr<ServiceWorkerCache> ServiceWorkerCache::AsWeakPtr() {
   return weak_ptr_factory_.GetWeakPtr();
 }
 
+void ServiceWorkerCache::CreateBackend(const ErrorCallback& callback) {
+  net::CacheType cache_type =
+      path_.empty() ? net::MEMORY_CACHE : net::DISK_CACHE;
+
+  net::CompletionCallback create_cache_callback =
+      base::Bind(&ServiceWorkerCache::CreateBackendDidCreate,
+                 base::Unretained(this),
+                 callback);
+  int rv = disk_cache::CreateCacheBackend(
+      cache_type,
+      net::CACHE_BACKEND_SIMPLE,
+      path_,
+      kMaxCacheBytes,
+      true, /* force */
+      BrowserThread::GetMessageLoopProxyForThread(BrowserThread::CACHE).get(),

[michaeln, 2014/08/14 10:35:20]

ServiceWorkerContextCore constructor has the cachethread mlp as an input. This
class should probably use that input too.

[jkarlin, 2014/08/14 19:53:32]

Agree, added a TODO to do that in another CL.

+      NULL,
+      &backend_,

[michaeln, 2014/08/14 10:35:20]

initialization is treacherous, i think if ServiceWorkerCache is deleted prior to
create cache completion, we could be trying to write to &backend_ after storage
for it is gone.

you've probably seen ServiceWorkerDiskCache ServiceWorkerResponseReader and
ServiceWorkerResponseWriter. these classes do what they sound like they do, are
well tested, and maybe could be applied here as well.

[jkarlin, 2014/08/14 19:53:33]

The ServiceWorkerCacheStorage::Delete(cache) can't be called until create cache
has completed.  Other forms of deletion (e.g., ServiceWorker closing) will cause
the ServiceWorkerCacheStorage to delete and so the callback won't run (due to
WeakPtr).
I'm all for consolidation.  Those classes rely on an (entry_name -> int64) key
conversion which I don't have or necessarily want however. Perhaps in the
future?

[michaeln1, 2014/08/14 22:57:09]

The callback won't get called but &backend_ is written to prior to invoking the
callback.

[jkarlin, 2014/08/15 11:49:44]

Done.

+      create_cache_callback);
+  if (rv != net::ERR_IO_PENDING)
+    CreateBackendDidCreate(callback, rv);
+}
+
+void ServiceWorkerCache::CreateBackendDidCreate(const ErrorCallback& callback,
+                                                int rv) {
+  if (rv != net::OK) {
+    callback.Run(ErrorTypeStorage);
+    return;
+  }
+  callback.Run(ErrorTypeOK);
+}
+
+void ServiceWorkerCache::Put(ServiceWorkerFetchRequest* request,
+                             ServiceWorkerResponse* response,
+                             const ErrorCallback& callback) {
+  DCHECK(backend_);
+
+  scoped_ptr<disk_cache::Entry*> entry(new disk_cache::Entry*);
+
+  disk_cache::Entry** entry_ptr = entry.get();
+
+  net::CompletionCallback create_entry_callback =
+      base::Bind(&ServiceWorkerCache::PutDidCreateEntry,
+                 base::Unretained(this),
+                 request,
+                 response,
+                 callback,
+                 base::Passed(entry.Pass()));
+
+  int rv = backend_->CreateEntry(
+      request->url.spec(), entry_ptr, create_entry_callback);
+
+  if (rv != net::ERR_IO_PENDING)
+    create_entry_callback.Run(rv);
+}
+
+void ServiceWorkerCache::Match(ServiceWorkerFetchRequest* request,
+                               const ResponseCallback& callback) {
+  DCHECK(backend_);
+
+  scoped_ptr<disk_cache::Entry*> entry(new disk_cache::Entry*);
+
+  disk_cache::Entry** entry_ptr = entry.get();
+
+  net::CompletionCallback open_entry_callback =
+      base::Bind(&ServiceWorkerCache::MatchDidOpenEntry,
+                 weak_ptr_factory_.GetWeakPtr(),
+                 request,
+                 callback,
+                 base::Passed(entry.Pass()));
+
+  int rv =
+      backend_->OpenEntry(request->url.spec(), entry_ptr, open_entry_callback);
+  if (rv != net::ERR_IO_PENDING)
+    open_entry_callback.Run(rv);
+}
+
+void ServiceWorkerCache::MatchDidOpenEntry(
+    ServiceWorkerFetchRequest* request,
+    const ResponseCallback& callback,
+    scoped_ptr<disk_cache::Entry*> entryptr,
+    int rv) {
+  if (rv != net::OK) {
+    callback.Run(ErrorNotFound,
+                 scoped_ptr<ServiceWorkerResponse>(),
+                 scoped_ptr<webkit_blob::BlobDataHandle>());
+    return;
+  }
+
+  DCHECK(entryptr);
+  disk_cache::Entry* entry = *entryptr;
+
+  scoped_refptr<net::IOBufferWithSize> buffer(
+      new net::IOBufferWithSize(entry->GetDataSize(INDEX_HEADERS)));
+
+  int read_rv =
+      entry->ReadData(INDEX_HEADERS,
+                      0,
+                      buffer.get(),
+                      buffer->size(),
+                      base::Bind(&ServiceWorkerCache::MatchDidReadHeaderData,
+                                 weak_ptr_factory_.GetWeakPtr(),
+                                 request,
+                                 callback,
+                                 base::Unretained(entry),

[michaeln, 2014/08/14 10:35:20]

if ServiceWorkerCache is deleted while in flight, is entry leaked?

[jkarlin, 2014/08/14 19:53:32]

Yes, thanks.  Hadn't gotten to all of the pointers yet.

+                                 buffer));
+  if (read_rv != net::ERR_IO_PENDING)
+    MatchDidReadHeaderData(request, callback, entry, buffer, read_rv);
+}
+
+void ServiceWorkerCache::MatchDidReadHeaderData(
+    ServiceWorkerFetchRequest* request,
+    const ResponseCallback& callback,
+    disk_cache::Entry* entry,
+    const scoped_refptr<net::IOBufferWithSize>& buffer,
+    int rv) {
+  if (rv != buffer->size()) {
+    entry->Close();
+    callback.Run(ErrorTypeStorage,
+                 scoped_ptr<ServiceWorkerResponse>(),
+                 scoped_ptr<webkit_blob::BlobDataHandle>());
+    return;
+  }
+
+  ServiceWorkerRequestResponseHeaders headers;
+
+  if (!headers.ParseFromArray(buffer->data(), buffer->size())) {
+    entry->Close();
+    callback.Run(ErrorTypeStorage,
+                 scoped_ptr<ServiceWorkerResponse>(),
+                 scoped_ptr<webkit_blob::BlobDataHandle>());
+    return;
+  }
+
+  scoped_ptr<ServiceWorkerResponse> response(
+      new ServiceWorkerResponse(request->url,
+                                headers.status_code(),
+                                headers.status_text(),
+                                std::map<std::string, std::string>(),
+                                ""));
+
+  for (int i = 0; i < headers.response_headers_size(); ++i) {
+    const ServiceWorkerRequestResponseHeaders::HeaderMap header =
+        headers.response_headers(i);
+    response->headers.insert(std::make_pair(header.name(), header.value()));
+  }
+
+  // TODO(jkarlin): Insert vary validation here.
+
+  if (entry->GetDataSize(INDEX_RESPONSE_BODY) == 0) {
+    entry->Close();
+    callback.Run(ErrorTypeOK,
+                 response.Pass(),
+                 scoped_ptr<webkit_blob::BlobDataHandle>());
+    return;
+  }
+
+  // Stream the response body into a blob.
+  if (!blob_storage_context_) {
+    entry->Close();
+    callback.Run(ErrorTypeStorage,
+                 scoped_ptr<ServiceWorkerResponse>(),
+                 scoped_ptr<webkit_blob::BlobDataHandle>());
+    return;
+  }
+
+  response->blob_uuid = base::GenerateGUID();
+
+  scoped_refptr<webkit_blob::BlobData> blob_data =
+      new webkit_blob::BlobData(response->blob_uuid);
+  scoped_refptr<net::IOBufferWithSize> response_body_buffer(
+      new net::IOBufferWithSize(kBufferSize));
+
+  scoped_ptr<ResponseReadContext> read_context(
+      new ResponseReadContext(response_body_buffer, blob_data));
+
+  net::CompletionCallback read_callback =
+      base::Bind(&ServiceWorkerCache::MatchDidReadResponseBodyData,
+                 weak_ptr_factory_.GetWeakPtr(),
+                 request,
+                 callback,
+                 base::Unretained(entry),
+                 base::Passed(response.Pass()),
+                 base::Passed(read_context.Pass()));
+
+  int read_rv = entry->ReadData(
+      INDEX_RESPONSE_BODY, 0, buffer.get(), buffer->size(), read_callback);
+
+  if (read_rv != net::ERR_IO_PENDING)
+    read_callback.Run(read_rv);
+}
+
+void ServiceWorkerCache::MatchDidReadResponseBodyData(
+    ServiceWorkerFetchRequest* request,
+    const ResponseCallback& callback,
+    disk_cache::Entry* entry,
+    scoped_ptr<ServiceWorkerResponse> response,
+    scoped_ptr<ResponseReadContext> response_context,
+    int rv) {
+  if (entry < 0) {
+    entry->Close();
+    callback.Run(ErrorTypeStorage,
+                 scoped_ptr<ServiceWorkerResponse>(),
+                 scoped_ptr<webkit_blob::BlobDataHandle>());
+  }
+
+  if (rv == 0) {
+    entry->Close();
+
+    MatchDoneWithBody(
+        request, callback, response.Pass(), response_context.Pass());
+    return;
+  }
+
+  // TODO(jkarlin): This copying of the the entire cache response into memory is
+  // awful. Create a new interface around SimpleCache that provides access the
+  // data directly from the file. See bug http://crbug.com/403493.
+  response_context->blob_data->AppendData(response_context->buffer->data(), rv);
+  response_context->total_bytes_read += rv;
+  int total_bytes_read = response_context->total_bytes_read;
+
+  LOG(ERROR) << "Reading: " << std::string(response_context->buffer->data(),
+                                           rv);
+  // Grab the pointer before response_context is Pass()ed.
+  net::IOBufferWithSize* buffer = response_context->buffer;
+
+  net::CompletionCallback read_callback =
+      base::Bind(&ServiceWorkerCache::MatchDidReadResponseBodyData,
+                 weak_ptr_factory_.GetWeakPtr(),
+                 request,
+                 callback,
+                 base::Unretained(entry),
+                 base::Passed(response.Pass()),
+                 base::Passed(response_context.Pass()));
+
+  int read_rv = entry->ReadData(INDEX_RESPONSE_BODY,
+                                total_bytes_read,
+                                buffer,
+                                buffer->size(),
+                                read_callback);
+
+  if (read_rv != net::ERR_IO_PENDING)
+    read_callback.Run(read_rv);
+}
+
+void ServiceWorkerCache::MatchDoneWithBody(
+    ServiceWorkerFetchRequest* request,
+    const ResponseCallback& callback,
+    scoped_ptr<ServiceWorkerResponse> response,
+    scoped_ptr<ResponseReadContext> response_context) {
+  // TODO(jkarlin): Create a blob and pass it back to the renderer. How do we
+  // reference count that?

[michaeln, 2014/08/14 10:35:20]

1) the uuid is sent from browser->renderer in the MatchResponse IPC
2) the renderer takes a reference when a blink::BlobDataHandle is constructed
over there
3) the renderer sends an 'ack' to the MatchResponse
4) upon receipt of the 'ack', the browser deletes the
webkit_blob::BlobDataHandle

[jkarlin, 2014/08/14 19:53:32]

Acknowledged.

+  if (!blob_storage_context_) {
+    callback.Run(ErrorTypeStorage,
+                 scoped_ptr<ServiceWorkerResponse>(),
+                 scoped_ptr<webkit_blob::BlobDataHandle>());
+    return;
+  }
+
+  scoped_ptr<webkit_blob::BlobDataHandle> blob_data_handle(
+      blob_storage_context_->AddFinishedBlob(
+          response_context->blob_data.get()));
+
+  callback.Run(ErrorTypeOK, response.Pass(), blob_data_handle.Pass());
+}
+
+void ServiceWorkerCache::PutDidCreateEntry(
+    ServiceWorkerFetchRequest* request,
+    ServiceWorkerResponse* response,
+    const ErrorCallback& callback,
+    scoped_ptr<disk_cache::Entry*> entryptr,
+    int rv) {
+  if (rv != net::OK) {
+    callback.Run(ErrorTypeExists);
+    return;
+  }
+
+  DCHECK(entryptr);
+  disk_cache::Entry* entry = *entryptr;
+
+  ServiceWorkerRequestResponseHeaders headers;
+  headers.set_method(request->method);
+
+  headers.set_status_code(response->status_code);
+  headers.set_status_text(response->status_text);
+  for (std::map<std::string, std::string>::const_iterator it =
+           request->headers.begin();
+       it != request->headers.end();
+       ++it) {
+    ServiceWorkerRequestResponseHeaders::HeaderMap* header_map =
+        headers.add_request_headers();
+    header_map->set_name(it->first);
+    header_map->set_value(it->second);
+  }
+
+  for (std::map<std::string, std::string>::const_iterator it =
+           response->headers.begin();
+       it != response->headers.end();
+       ++it) {
+    ServiceWorkerRequestResponseHeaders::HeaderMap* header_map =
+        headers.add_response_headers();
+    header_map->set_name(it->first);
+    header_map->set_value(it->second);
+  }
+
+  scoped_refptr<net::ZeroCopyStringIOBuffer> buffer(

[michaeln, 2014/08/14 10:35:20]

would it make sense for the existing StringIOBuffer class to have a ctor that
used std::string::swap on the string provided to zerocopy it into the iobuffer?

[jkarlin, 2014/08/14 19:53:33]

I like the idea of using std::string:swap.  I changed the zerocopy class to use
that instead.  Given the various uses of StringIOBuffer today I'd rather
introduce this new function than change the old.  We could (and should)
deprecate the old one however.

+      new net::ZeroCopyStringIOBuffer());
+  if (!headers.SerializeToString(buffer->string())) {
+    callback.Run(ErrorTypeStorage);
+  }
+
+  buffer->Done();
+
+  net::CompletionCallback write_headers_callback =
+      base::Bind(&ServiceWorkerCache::PutDidWriteHeaders,
+                 weak_ptr_factory_.GetWeakPtr(),
+                 request,
+                 response,
+                 callback,
+                 entry,
+                 buffer->string()->size());
+
+  rv = entry->WriteData(INDEX_HEADERS,
+                        0 /* offset */,
+                        buffer,
+                        buffer->string()->size(),
+                        write_headers_callback,
+                        true /* truncate */);
+
+  if (rv != net::ERR_IO_PENDING)
+    write_headers_callback.Run(rv);
+}
+
+void ServiceWorkerCache::PutDidWriteHeaders(ServiceWorkerFetchRequest* request,
+                                            ServiceWorkerResponse* response,
+                                            const ErrorCallback& callback,
+                                            disk_cache::Entry* entry,
+                                            int expected_bytes,
+                                            int rv) {
+  if (rv != expected_bytes) {
+    entry->Doom();
+    entry->Close();
+    callback.Run(ErrorTypeStorage);
+    return;
+  }
+
+  // The metadata is written, now for the response content. The data is streamed
+  // from the blob into the cache entry.
+
+  if (response->blob_uuid.empty()) {
+    entry->Close();
+    callback.Run(ErrorTypeOK);
+    return;
+  }
+
+  if (!blob_storage_context_) {
+    entry->Doom();
+    entry->Close();
+    callback.Run(ErrorTypeStorage);
+    return;
+  }
+
+  scoped_ptr<webkit_blob::BlobDataHandle> blob_data_handle =
+      blob_storage_context_->GetBlobDataFromUUID(response->blob_uuid);

[michaeln, 2014/08/14 10:35:20]

you should get this handle up front in ServiceWorkerCache::Put() otherwise
there's no guarantee it hasn't been gc'd by the time this is reached. The
webkit_blob::BlobDataHandle should be gotten prior to return from IPC handler
for the PUT message.

[jkarlin, 2014/08/14 19:53:32]

Thanks! Done and added test.

+
+  if (!blob_data_handle) {
+    entry->Doom();
+    entry->Close();
+    callback.Run(ErrorTypeStorage);
+    return;
+  }
+
+  scoped_ptr<BlobReader> reader(new BlobReader(entry));
+
+  reader->StreamBlobToCache(
+      request_context_,
+      blob_data_handle.Pass(),
+      base::Bind(&ServiceWorkerCache::PutDidWriteBlobToCache,
+                 weak_ptr_factory_.GetWeakPtr(),
+                 callback,
+                 entry,

[michaeln, 2014/08/14 10:35:20]

if ServiceWorkerCache is deleted prior to completion, entry will not be closed
(leak?)

[jkarlin, 2014/08/14 19:53:33]

Done.

+                 base::Passed(reader.Pass())));
+}
+
+void ServiceWorkerCache::PutDidWriteBlobToCache(
+    const ErrorCallback& callback,
+    disk_cache::Entry* entry,
+    scoped_ptr<BlobReader> blob_reader,
+    bool success) {
+  if (!success) {
+    entry->Doom();
+    entry->Close();
+    callback.Run(ErrorTypeStorage);
+    return;
+  }
+
+  entry->Close();
+  callback.Run(ErrorTypeOK);
+}
+
 ServiceWorkerCache::ServiceWorkerCache(
     const base::FilePath& path,
     const std::string& name,
@@ -53,7 +588,4 @@ ServiceWorkerCache::ServiceWorkerCache(
       weak_ptr_factory_(this) {
 }
 
-ServiceWorkerCache::~ServiceWorkerCache() {
-}
-
 }  // namespace content