[CacheStorage] Pad and bin opaque resource sizes.

content/browser/cache_storage/cache_storage_cache.cc

Index: content/browser/cache_storage/cache_storage_cache.cc
diff --git a/content/browser/cache_storage/cache_storage_cache.cc b/content/browser/cache_storage/cache_storage_cache.cc
index d8729778100f13d774841c0eb0093df128c7e961..a48ed042054e2e639187b095e7f7fe74612a39ad 100644
--- a/content/browser/cache_storage/cache_storage_cache.cc
+++ b/content/browser/cache_storage/cache_storage_cache.cc
@@ -6,6 +6,7 @@
 
 #include <stddef.h>
 #include <algorithm>
+#include <functional>
 #include <limits>
 #include <memory>
 #include <string>
@@ -29,6 +30,8 @@
 #include "content/public/browser/browser_thread.h"
 #include "content/public/common/content_features.h"
 #include "content/public/common/referrer.h"
+#include "crypto/hmac.h"
+#include "crypto/symmetric_key.h"
 #include "net/base/completion_callback.h"
 #include "net/base/io_buffer.h"
 #include "net/base/net_errors.h"
@@ -260,6 +263,78 @@ std::unique_ptr<ServiceWorkerResponse> CreateResponse(
           metadata.response().cors_exposed_header_names().end()));
 }
 
+// The size of opaque (non-cors) resource responses are padded in order
+// to obfuscate their actual size.
+bool ShouldPadResponseType(network::mojom::FetchResponseType response_type,
+                           bool has_urls) {
+  switch (response_type) {
+    case network::mojom::FetchResponseType::kBasic:
+    case network::mojom::FetchResponseType::kCORS:
+    case network::mojom::FetchResponseType::kDefault:
+    case network::mojom::FetchResponseType::kError:
+      return false;
+    case network::mojom::FetchResponseType::kOpaque:
+    case network::mojom::FetchResponseType::kOpaqueRedirect:
+      return has_urls;
+  }
+  NOTREACHED();
+  return false;
+}
+
+bool ShouldPadResourceSize(const content::proto::CacheResponse* response) {
+  return ShouldPadResponseType(
+      ProtoResponseTypeToFetchResponseType(response->response_type()),
+      response->url_list_size());
+}
+
+bool ShouldPadResourceSize(const ServiceWorkerResponse* response) {
+  return ShouldPadResponseType(response->response_type,
+                               !response->url_list.empty());
+}
+
+// If the way that a cache's padding is calculated changes increment this
+// version.
+//
+// History:
+//
+//   1: Uniform random 400K.
+const int32_t kCachePaddingAlgorithmVersion = 1;
+
+int64_t CalculateResponsePaddingInternal(
+    const std::string& response_url,
+    const crypto::SymmetricKey* padding_key,
+    int side_data_size) {
+  const uint64_t kPaddingRange = 400 * 1024;  // Increment version if changed.
+
+  DCHECK(!response_url.empty());
+
+  crypto::HMAC hmac(crypto::HMAC::SHA256);
+  if (!hmac.Init(padding_key))
+    LOG(FATAL) << "Failed to init HMAC.";
+
+  std::vector<uint8_t> digest(hmac.DigestLength());
+  bool success;
+  if (side_data_size)
+    success = hmac.Sign(response_url + "METADATA", &digest[0], digest.size());
+  else
+    success = hmac.Sign(response_url, &digest[0], digest.size());
+  if (!success)
+    LOG(FATAL) << "Failed to sign URL.";
+
+  DCHECK_GE(digest.size(), sizeof(uint64_t));
+  uint64_t val = *(reinterpret_cast<uint64_t*>(&digest[0]));
+  return val % kPaddingRange;
+}
+
+int64_t CalculateResponsePaddingInternal(
+    const ::content::proto::CacheResponse* response,
+    const crypto::SymmetricKey* padding_key,
+    int side_data_size) {
+  DCHECK(ShouldPadResourceSize(response));
+  const std::string& url = response->url_list(response->url_list_size() - 1);
+  return CalculateResponsePaddingInternal(url, padding_key, side_data_size);
+}
+
 }  // namespace
 
 // The state needed to pass between CacheStorageCache::Put callbacks.
@@ -297,10 +372,12 @@ struct CacheStorageCache::QueryCacheResult {
 struct CacheStorageCache::QueryCacheContext {
   QueryCacheContext(std::unique_ptr<ServiceWorkerFetchRequest> request,
                     const CacheStorageCacheQueryParams& options,
-                    QueryCacheCallback callback)
+                    QueryCacheCallback callback,
+                    QueryTypes query_types)
       : request(std::move(request)),
         options(options),
         callback(std::move(callback)),
+        query_types(query_types),
         matches(base::MakeUnique<QueryCacheResults>()) {}
 
   ~QueryCacheContext() {
@@ -317,7 +394,7 @@ struct CacheStorageCache::QueryCacheContext {
   std::unique_ptr<ServiceWorkerFetchRequest> request;
   CacheStorageCacheQueryParams options;
   QueryCacheCallback callback;
-  QueryCacheType query_type;
+  QueryTypes query_types = 0;
   size_t estimated_out_bytes = 0;
 
   // Iteration state
@@ -338,11 +415,13 @@ std::unique_ptr<CacheStorageCache> CacheStorageCache::CreateMemoryCache(
     CacheStorage* cache_storage,
     scoped_refptr<net::URLRequestContextGetter> request_context_getter,
     scoped_refptr<storage::QuotaManagerProxy> quota_manager_proxy,
-    base::WeakPtr<storage::BlobStorageContext> blob_context) {
+    base::WeakPtr<storage::BlobStorageContext> blob_context,
+    std::unique_ptr<crypto::SymmetricKey> cache_padding_key) {
   CacheStorageCache* cache = new CacheStorageCache(
       origin, cache_name, base::FilePath(), cache_storage,
       std::move(request_context_getter), std::move(quota_manager_proxy),
-      blob_context, 0 /* cache_size */);
+      blob_context, 0 /* cache_size */, 0 /* cache_padding */,
+      std::move(cache_padding_key));
   cache->SetObserver(cache_storage);
   cache->InitBackend();
   return base::WrapUnique(cache);
@@ -357,11 +436,13 @@ std::unique_ptr<CacheStorageCache> CacheStorageCache::CreatePersistentCache(
     scoped_refptr<net::URLRequestContextGetter> request_context_getter,
     scoped_refptr<storage::QuotaManagerProxy> quota_manager_proxy,
     base::WeakPtr<storage::BlobStorageContext> blob_context,
-    int64_t cache_size) {
+    int64_t cache_size,
+    int64_t cache_padding,
+    std::unique_ptr<crypto::SymmetricKey> cache_padding_key) {
   CacheStorageCache* cache = new CacheStorageCache(
       origin, cache_name, path, cache_storage,
       std::move(request_context_getter), std::move(quota_manager_proxy),
-      blob_context, cache_size);
+      blob_context, cache_size, cache_padding, std::move(cache_padding_key));
   cache->SetObserver(cache_storage), cache->InitBackend();
   return base::WrapUnique(cache);
 }
@@ -607,7 +688,9 @@ CacheStorageCache::CacheStorageCache(
     scoped_refptr<net::URLRequestContextGetter> request_context_getter,
     scoped_refptr<storage::QuotaManagerProxy> quota_manager_proxy,
     base::WeakPtr<storage::BlobStorageContext> blob_context,
-    int64_t cache_size)
+    int64_t cache_size,
+    int64_t cache_padding,
+    std::unique_ptr<crypto::SymmetricKey> cache_padding_key)
     : origin_(origin),
       cache_name_(cache_name),
       path_(path),
@@ -618,12 +701,15 @@ CacheStorageCache::CacheStorageCache(
       scheduler_(
           new CacheStorageScheduler(CacheStorageSchedulerClient::CLIENT_CACHE)),
       cache_size_(cache_size),
+      cache_padding_(cache_padding),
+      cache_padding_key_(std::move(cache_padding_key)),
       max_query_size_bytes_(kMaxQueryCacheResultBytes),
       cache_observer_(nullptr),
       memory_only_(path.empty()),
       weak_ptr_factory_(this) {
   DCHECK(!origin_.is_empty());
   DCHECK(quota_manager_proxy_.get());
+  DCHECK(cache_padding_key_.get());
 
   quota_manager_proxy_->NotifyOriginInUse(origin_);
 }
@@ -631,10 +717,12 @@ CacheStorageCache::CacheStorageCache(
 void CacheStorageCache::QueryCache(
     std::unique_ptr<ServiceWorkerFetchRequest> request,
     const CacheStorageCacheQueryParams& options,
-    QueryCacheType query_type,
+    QueryTypes query_types,
     QueryCacheCallback callback) {
-  DCHECK_NE(BACKEND_UNINITIALIZED, backend_state_);
-  if (backend_state_ != BACKEND_OPEN) {
+  DCHECK_NE(
+      QUERY_CACHE_ENTRIES | QUERY_CACHE_RESPONSES_WITH_BODIES,
+      query_types & (QUERY_CACHE_ENTRIES | QUERY_CACHE_RESPONSES_WITH_BODIES));
+  if (backend_state_ == BACKEND_CLOSED) {
     std::move(callback).Run(CACHE_STORAGE_ERROR_STORAGE,
                             std::unique_ptr<QueryCacheResults>());
     return;
@@ -648,9 +736,8 @@ void CacheStorageCache::QueryCache(
   }
 
   ServiceWorkerFetchRequest* request_ptr = request.get();
-  std::unique_ptr<QueryCacheContext> query_cache_context(
-      new QueryCacheContext(std::move(request), options, std::move(callback)));
-  query_cache_context->query_type = query_type;
+  std::unique_ptr<QueryCacheContext> query_cache_context(new QueryCacheContext(
+      std::move(request), options, std::move(callback), query_types));
 
   if (query_cache_context->request &&
       !query_cache_context->request->url.is_empty() && !options.ignore_search) {
@@ -733,7 +820,7 @@ void CacheStorageCache::QueryCacheFilterEntry(
   disk_cache::ScopedEntryPtr entry(query_cache_context->enumerated_entry);
   query_cache_context->enumerated_entry = nullptr;
 
-  if (backend_state_ != BACKEND_OPEN) {
+  if (backend_state_ == BACKEND_CLOSED) {
     std::move(query_cache_context->callback)
         .Run(CACHE_STORAGE_ERROR_NOT_FOUND,
              std::move(query_cache_context->matches));
@@ -795,57 +882,50 @@ void CacheStorageCache::QueryCacheDidReadMetadata(
     return;
   }
 
-  if (query_cache_context->query_type == QueryCacheType::CACHE_ENTRIES) {
-    match->request.reset();
-    match->response.reset();
+  if (query_cache_context->query_types & QUERY_CACHE_ENTRIES)
     match->entry = std::move(entry);
-    QueryCacheOpenNextEntry(std::move(query_cache_context));
-    return;
-  }
 
-  query_cache_context->estimated_out_bytes +=
-      match->request->EstimatedStructSize();
-  if (query_cache_context->estimated_out_bytes > max_query_size_bytes_) {
-    std::move(query_cache_context->callback)
-        .Run(CACHE_STORAGE_ERROR_QUERY_TOO_LARGE,
-             std::unique_ptr<QueryCacheResults>());
-    return;
-  }
-
-  if (query_cache_context->query_type == QueryCacheType::REQUESTS) {
-    match->response.reset();
-    QueryCacheOpenNextEntry(std::move(query_cache_context));
-    return;
+  if (query_cache_context->query_types & QUERY_CACHE_REQUESTS) {
+    query_cache_context->estimated_out_bytes +=
+        match->request->EstimatedStructSize();
+    if (query_cache_context->estimated_out_bytes > max_query_size_bytes_) {
+      std::move(query_cache_context->callback)
+          .Run(CACHE_STORAGE_ERROR_QUERY_TOO_LARGE,
+               std::unique_ptr<QueryCacheResults>());
+      return;
+    }
+  } else {
+    match->request.reset();
   }
 
-  DCHECK_EQ(QueryCacheType::REQUESTS_AND_RESPONSES,
-            query_cache_context->query_type);
-
-  query_cache_context->estimated_out_bytes +=
-      match->response->EstimatedStructSize();
-  if (query_cache_context->estimated_out_bytes > max_query_size_bytes_) {
-    std::move(query_cache_context->callback)
-        .Run(CACHE_STORAGE_ERROR_QUERY_TOO_LARGE,
-             std::unique_ptr<QueryCacheResults>());
-    return;
-  }
+  if (query_cache_context->query_types & QUERY_CACHE_RESPONSES_WITH_BODIES) {
+    query_cache_context->estimated_out_bytes +=
+        match->response->EstimatedStructSize();
+    if (query_cache_context->estimated_out_bytes > max_query_size_bytes_) {
+      std::move(query_cache_context->callback)
+          .Run(CACHE_STORAGE_ERROR_QUERY_TOO_LARGE,
+               std::unique_ptr<QueryCacheResults>());
+      return;
+    }
+    if (entry->GetDataSize(INDEX_RESPONSE_BODY) == 0) {
+      QueryCacheOpenNextEntry(std::move(query_cache_context));
+      return;
+    }
 
-  if (entry->GetDataSize(INDEX_RESPONSE_BODY) == 0) {
-    QueryCacheOpenNextEntry(std::move(query_cache_context));
-    return;
-  }
+    if (!blob_storage_context_) {
+      std::move(query_cache_context->callback)
+          .Run(CACHE_STORAGE_ERROR_STORAGE,
+               std::unique_ptr<QueryCacheResults>());
+      return;
+    }
 
-  if (!blob_storage_context_) {
-    std::move(query_cache_context->callback)
-        .Run(CACHE_STORAGE_ERROR_STORAGE,
-             base::MakeUnique<QueryCacheResults>());
-    return;
+    match->blob_handle =
+        PopulateResponseBody(std::move(entry), match->response.get());
+  } else if (!(query_cache_context->query_types &
+               QUERY_CACHE_RESPONSES_NO_BODIES)) {
+    match->response.reset();
   }
 
-  std::unique_ptr<storage::BlobDataHandle> blob_data_handle =
-      PopulateResponseBody(std::move(entry), match->response.get());
-  match->blob_handle = std::move(blob_data_handle);
-
   QueryCacheOpenNextEntry(std::move(query_cache_context));
 }
 
@@ -855,6 +935,22 @@ bool CacheStorageCache::QueryCacheResultCompare(const QueryCacheResult& lhs,
   return lhs.entry_time < rhs.entry_time;
 }
 
+// static
+int64_t CacheStorageCache::CalculateResponsePadding(
+    const ServiceWorkerResponse& response,
+    const crypto::SymmetricKey* padding_key,
+    int side_data_size) {
+  if (!ShouldPadResourceSize(&response))
+    return 0;
+  return CalculateResponsePaddingInternal(response.url_list.back().spec(),
+                                          padding_key, side_data_size);
+}
+
+// static
+int32_t CacheStorageCache::GetResponsePaddingVersion() {
+  return kCachePaddingAlgorithmVersion;
+}
+
 void CacheStorageCache::MatchImpl(
     std::unique_ptr<ServiceWorkerFetchRequest> request,
     const CacheStorageCacheQueryParams& match_params,
@@ -904,7 +1000,8 @@ void CacheStorageCache::MatchAllImpl(
   }
 
   QueryCache(
-      std::move(request), options, QueryCacheType::REQUESTS_AND_RESPONSES,
+      std::move(request), options,
+      QUERY_CACHE_REQUESTS | QUERY_CACHE_RESPONSES_WITH_BODIES,
       base::BindOnce(&CacheStorageCache::MatchAllDidQueryCache,
                      weak_ptr_factory_.GetWeakPtr(), std::move(callback)));
 }
@@ -1017,11 +1114,19 @@ void CacheStorageCache::WriteSideDataDidReadMetaData(
   // Get a temporary copy of the entry pointer before passing it in base::Bind.
   disk_cache::Entry* temp_entry_ptr = entry.get();
 
+  std::unique_ptr<content::proto::CacheResponse> response(
+      headers->release_response());
+
+  int side_data_size_before_write = 0;
+  if (ShouldPadResourceSize(response.get()))
+    side_data_size_before_write = entry->GetDataSize(INDEX_SIDE_DATA);
+
   net::CompletionCallback write_side_data_callback =
       base::AdaptCallbackForRepeating(
           base::BindOnce(&CacheStorageCache::WriteSideDataDidWrite,
                          weak_ptr_factory_.GetWeakPtr(), std::move(callback),
-                         base::Passed(std::move(entry)), buf_len));
+                         base::Passed(std::move(entry)), buf_len,
+                         std::move(response), side_data_size_before_write));
 
   int rv = temp_entry_ptr->WriteData(
       INDEX_SIDE_DATA, 0 /* offset */, buffer.get(), buf_len,
@@ -1031,10 +1136,13 @@ void CacheStorageCache::WriteSideDataDidReadMetaData(
     write_side_data_callback.Run(rv);
 }
 
-void CacheStorageCache::WriteSideDataDidWrite(ErrorCallback callback,
-                                              disk_cache::ScopedEntryPtr entry,
-                                              int expected_bytes,
-                                              int rv) {
+void CacheStorageCache::WriteSideDataDidWrite(
+    ErrorCallback callback,
+    disk_cache::ScopedEntryPtr entry,
+    int expected_bytes,
+    std::unique_ptr<::content::proto::CacheResponse> response,
+    int side_data_size_before_write,
+    int rv) {
   if (rv != expected_bytes) {
     entry->Doom();
     UpdateCacheSize(
@@ -1045,6 +1153,14 @@ void CacheStorageCache::WriteSideDataDidWrite(ErrorCallback callback,
   if (rv > 0)
     storage::RecordBytesWritten(kRecordBytesLabel, rv);
 
+  if (ShouldPadResourceSize(response.get())) {
+    cache_padding_ -= CalculateResponsePaddingInternal(
+        response.get(), cache_padding_key_.get(), side_data_size_before_write);
+
+    cache_padding_ += CalculateResponsePaddingInternal(
+        response.get(), cache_padding_key_.get(), rv);
+  }
+
   UpdateCacheSize(base::BindOnce(std::move(callback), CACHE_STORAGE_OK));
 }
 
@@ -1099,26 +1215,36 @@ void CacheStorageCache::PutImpl(std::unique_ptr<PutContext> put_context) {
     return;
   }
 
-  std::string key = put_context->request->url.spec();
+  // Explicitly delete the incumbent resource (which may not exist). This is
+  // only done so that it's padding will be decremented from the calculated
+  // cache padding.
+  // TODO(cmumford): Research alternatives to this explicit delete as it
+  // seriously impacts put performance.
+  auto delete_request = base::MakeUnique<ServiceWorkerFetchRequest>(
+      put_context->request->url, "", ServiceWorkerHeaderMap(), Referrer(),
+      false);
 
-  net::CompletionCallback callback =
-      base::AdaptCallbackForRepeating(base::BindOnce(
-          &CacheStorageCache::PutDidDoomEntry, weak_ptr_factory_.GetWeakPtr(),
-          base::Passed(std::move(put_context))));
-
-  int rv = backend_->DoomEntry(key, callback);
-  if (rv != net::ERR_IO_PENDING)
-    callback.Run(rv);
+  CacheStorageCacheQueryParams query_options;
+  query_options.ignore_method = true;
+  query_options.ignore_vary = true;
+  DeleteImpl(std::move(delete_request), query_options,
+             base::BindOnce(&CacheStorageCache::PutDidDeleteEntry,
+                            weak_ptr_factory_.GetWeakPtr(),
+                            base::Passed(std::move(put_context))));
 }
 
-void CacheStorageCache::PutDidDoomEntry(std::unique_ptr<PutContext> put_context,
-                                        int rv) {
+void CacheStorageCache::PutDidDeleteEntry(
+    std::unique_ptr<PutContext> put_context,
+    CacheStorageError error) {
   if (backend_state_ != BACKEND_OPEN) {
     std::move(put_context->callback).Run(CACHE_STORAGE_ERROR_STORAGE);
     return;
   }
 
-  // |rv| is ignored as doom entry can fail if the entry doesn't exist.
+  if (error != CACHE_STORAGE_OK && error != CACHE_STORAGE_ERROR_NOT_FOUND) {
+    std::move(put_context->callback).Run(error);
+    return;
+  }
 
   std::unique_ptr<disk_cache::Entry*> scoped_entry_ptr(
       new disk_cache::Entry*());
@@ -1132,11 +1258,11 @@ void CacheStorageCache::PutDidDoomEntry(std::unique_ptr<PutContext> put_context,
           base::Passed(std::move(scoped_entry_ptr)),
           base::Passed(std::move(put_context))));
 
-  int create_rv = backend_ptr->CreateEntry(request_ptr->url.spec(), entry_ptr,
-                                           create_entry_callback);
+  int rv = backend_ptr->CreateEntry(request_ptr->url.spec(), entry_ptr,
+                                    create_entry_callback);
 
-  if (create_rv != net::ERR_IO_PENDING)
-    create_entry_callback.Run(create_rv);
+  if (rv != net::ERR_IO_PENDING)
+    create_entry_callback.Run(rv);
 }
 
 void CacheStorageCache::PutDidCreateEntry(
@@ -1223,6 +1349,11 @@ void CacheStorageCache::PutDidWriteHeaders(
 
   if (rv > 0)
     storage::RecordBytesWritten(kRecordBytesLabel, rv);
+  if (ShouldPadResourceSize(put_context->response.get())) {
+    cache_padding_ += CalculateResponsePadding(*put_context->response,
+                                               cache_padding_key_.get(),
+                                               0 /* side_data_size */);
+  }
 
   // The metadata is written, now for the response content. The data is streamed
   // from the blob into the cache entry.
@@ -1274,6 +1405,60 @@ void CacheStorageCache::PutDidWriteBlobToCache(
       base::BindOnce(std::move(put_context->callback), CACHE_STORAGE_OK));
 }
 
+void CacheStorageCache::CalculateCacheSizePadding(
+    SizePaddingCallback got_sizes_callback) {
+  net::CompletionCallback got_size_callback =
+      base::AdaptCallbackForRepeating(base::BindOnce(
+          &CacheStorageCache::CalculateCacheSizePaddingGotSize,
+          weak_ptr_factory_.GetWeakPtr(), std::move(got_sizes_callback)));
+
+  int rv = backend_->CalculateSizeOfAllEntries(got_size_callback);
+  if (rv != net::ERR_IO_PENDING)
+    got_size_callback.Run(rv);
+}
+
+void CacheStorageCache::CalculateCacheSizePaddingGotSize(
+    SizePaddingCallback callback,
+    int cache_size) {
+  // Enumerating entries is only done during cache initialization and only if
+  // necessary.
+  DCHECK_EQ(backend_state_, BACKEND_UNINITIALIZED);
+  std::unique_ptr<ServiceWorkerFetchRequest> request;
+  CacheStorageCacheQueryParams options;
+  options.ignore_search = true;
+  QueryCache(std::move(request), options, QUERY_CACHE_RESPONSES_NO_BODIES,
+             base::BindOnce(&CacheStorageCache::PaddingDidQueryCache,
+                            weak_ptr_factory_.GetWeakPtr(), std::move(callback),
+                            cache_size));
+}
+
+void CacheStorageCache::PaddingDidQueryCache(
+    SizePaddingCallback callback,
+    int cache_size,
+    CacheStorageError error,
+    std::unique_ptr<QueryCacheResults> query_cache_results) {
+  int64_t cache_padding = 0;
+  if (error == CACHE_STORAGE_OK) {
+    for (const auto& result : *query_cache_results) {
+      if (ShouldPadResourceSize(result.response.get())) {
+        int32_t side_data_size =
+            result.entry ? result.entry->GetDataSize(INDEX_SIDE_DATA) : 0;
+        cache_padding += CalculateResponsePadding(
+            *result.response, cache_padding_key_.get(), side_data_size);
+      }
+    }
+  }
+
+  std::move(callback).Run(cache_size, cache_padding);
+}
+
+void CacheStorageCache::CalculateCacheSize(
+    const net::CompletionCallback& callback) {
+  int rv = backend_->CalculateSizeOfAllEntries(callback);
+  if (rv != net::ERR_IO_PENDING)
+    callback.Run(rv);
+}
+
 void CacheStorageCache::UpdateCacheSize(base::OnceClosure callback) {
   if (backend_state_ != BACKEND_OPEN)
     return;
@@ -1281,14 +1466,10 @@ void CacheStorageCache::UpdateCacheSize(base::OnceClosure callback) {
   // Note that the callback holds a cache handle to keep the cache alive during
   // the operation since this UpdateCacheSize is often run after an operation
   // completes and runs its callback.
-  net::CompletionCallback size_callback = base::AdaptCallbackForRepeating(
+  CalculateCacheSize(base::AdaptCallbackForRepeating(
       base::BindOnce(&CacheStorageCache::UpdateCacheSizeGotSize,
                      weak_ptr_factory_.GetWeakPtr(),
-                     base::Passed(CreateCacheHandle()), std::move(callback)));
-
-  int rv = backend_->CalculateSizeOfAllEntries(size_callback);
-  if (rv != net::ERR_IO_PENDING)
-    std::move(size_callback).Run(rv);
+                     base::Passed(CreateCacheHandle()), std::move(callback))));
 }
 
 void CacheStorageCache::UpdateCacheSizeGotSize(
@@ -1296,17 +1477,16 @@ void CacheStorageCache::UpdateCacheSizeGotSize(
     base::OnceClosure callback,
     int current_cache_size) {
   DCHECK_NE(current_cache_size, CacheStorage::kSizeUnknown);
-  int64_t old_cache_size = cache_size_;
   cache_size_ = current_cache_size;
-
-  int64_t size_delta = current_cache_size - old_cache_size;
+  int64_t size_delta = PaddedCacheSize() - last_reported_size_;
+  last_reported_size_ = PaddedCacheSize();
 
   quota_manager_proxy_->NotifyStorageModified(
       storage::QuotaClient::kServiceWorkerCache, origin_,
       storage::kStorageTypeTemporary, size_delta);
 
   if (cache_observer_)
-    cache_observer_->CacheSizeUpdated(this, current_cache_size);
+    cache_observer_->CacheSizeUpdated(this);
 
   std::move(callback).Run();
 }
@@ -1340,7 +1520,8 @@ void CacheStorageCache::DeleteImpl(
   }
 
   QueryCache(
-      std::move(request), match_params, QueryCacheType::CACHE_ENTRIES,
+      std::move(request), match_params,
+      QUERY_CACHE_ENTRIES | QUERY_CACHE_RESPONSES_NO_BODIES,
       base::BindOnce(&CacheStorageCache::DeleteDidQueryCache,
                      weak_ptr_factory_.GetWeakPtr(), std::move(callback)));
 }
@@ -1361,6 +1542,11 @@ void CacheStorageCache::DeleteDidQueryCache(
 
   for (auto& result : *query_cache_results) {
     disk_cache::ScopedEntryPtr entry = std::move(result.entry);
+    if (ShouldPadResourceSize(result.response.get())) {
+      cache_padding_ -=
+          CalculateResponsePadding(*result.response, cache_padding_key_.get(),
+                                   entry->GetDataSize(INDEX_SIDE_DATA));
+    }
     entry->Doom();
   }
 
@@ -1379,7 +1565,7 @@ void CacheStorageCache::KeysImpl(
   }
 
   QueryCache(
-      std::move(request), options, QueryCacheType::REQUESTS,
+      std::move(request), options, QUERY_CACHE_REQUESTS,
       base::BindOnce(&CacheStorageCache::KeysDidQueryCache,
                      weak_ptr_factory_.GetWeakPtr(), std::move(callback)));
 }
@@ -1419,7 +1605,14 @@ void CacheStorageCache::DeleteBackendCompletedIO() {
 void CacheStorageCache::SizeImpl(SizeCallback callback) {
   DCHECK_NE(BACKEND_UNINITIALIZED, backend_state_);
 
-  int64_t size = backend_state_ == BACKEND_OPEN ? cache_size_ : 0;
+  // TODO(cmumford): Can CacheStorage::kSizeUnknown be returned instead of zero?
+  if (backend_state_ != BACKEND_OPEN) {
+    base::ThreadTaskRunnerHandle::Get()->PostTask(
+        FROM_HERE, base::BindOnce(std::move(callback), 0));
+    return;
+  }
+
+  int64_t size = backend_state_ == BACKEND_OPEN ? PaddedCacheSize() : 0;
   base::ThreadTaskRunnerHandle::Get()->PostTask(
       FROM_HERE, base::BindOnce(std::move(callback), size));
 }
@@ -1492,14 +1685,14 @@ void CacheStorageCache::InitDidCreateBackend(
     return;
   }
 
-  net::CompletionCallback size_callback =
-      base::AdaptCallbackForRepeating(base::BindOnce(
-          &CacheStorageCache::InitGotCacheSize, weak_ptr_factory_.GetWeakPtr(),
-          std::move(callback), cache_create_error));
+  auto calculate_size_callback =
+      base::AdaptCallbackForRepeating(std::move(callback));
+  int rv = backend_->CalculateSizeOfAllEntries(base::Bind(
+      &CacheStorageCache::InitGotCacheSize, weak_ptr_factory_.GetWeakPtr(),
+      calculate_size_callback, cache_create_error));
 
-  int rv = backend_->CalculateSizeOfAllEntries(size_callback);
   if (rv != net::ERR_IO_PENDING)
-    std::move(size_callback).Run(rv);
+    InitGotCacheSize(calculate_size_callback, cache_create_error, rv);
 }
 
 void CacheStorageCache::InitGotCacheSize(base::OnceClosure callback,
@@ -1515,10 +1708,41 @@ void CacheStorageCache::InitGotCacheSize(base::OnceClosure callback,
         << " does not match size from index: " << cache_size_;
     UMA_HISTOGRAM_COUNTS_10M("ServiceWorkerCache.IndexSizeDifference",
                              std::abs(cache_size_ - cache_size));
-    // Disabled for crbug.com/681900.
-    // DCHECK_EQ(cache_size_, cache_size);
+    if (cache_size_ != cache_size) {
+      // We assume that if the sizes match then then cached padding is still
+      // correct. If not then we recalculate the padding.
+      CalculateCacheSizePaddingGotSize(
+          base::BindOnce(&CacheStorageCache::InitGotCacheSizeAndPadding,
+                         weak_ptr_factory_.GetWeakPtr(), std::move(callback),
+                         cache_create_error),
+          cache_size);
+      return;
+    }
   }
+
+  if (cache_padding_ == CacheStorage::kSizeUnknown || cache_padding_ < 0) {
+    CalculateCacheSizePaddingGotSize(
+        base::BindOnce(&CacheStorageCache::InitGotCacheSizeAndPadding,
+                       weak_ptr_factory_.GetWeakPtr(), std::move(callback),
+                       cache_create_error),
+        cache_size);
+    return;
+  }
+
+  // If cached size matches actual size then assume cached padding is still
+  // correct.
+  InitGotCacheSizeAndPadding(std::move(callback), cache_create_error,
+                             cache_size, cache_padding_);
+}
+
+void CacheStorageCache::InitGotCacheSizeAndPadding(
+    base::OnceClosure callback,
+    CacheStorageError cache_create_error,
+    int64_t cache_size,
+    int64_t cache_padding) {
   cache_size_ = cache_size;
+  cache_padding_ = cache_padding;
+
   initializing_ = false;
   backend_state_ = (cache_create_error == CACHE_STORAGE_OK && backend_ &&
                     backend_state_ == BACKEND_UNINITIALIZED)
@@ -1529,7 +1753,7 @@ void CacheStorageCache::InitGotCacheSize(base::OnceClosure callback,
                             cache_create_error, CACHE_STORAGE_ERROR_LAST + 1);
 
   if (cache_observer_)
-    cache_observer_->CacheSizeUpdated(this, cache_size_);
+    cache_observer_->CacheSizeUpdated(this);
 
   std::move(callback).Run();
 }
@@ -1567,4 +1791,13 @@ CacheStorageCache::CreateCacheHandle() {
   return cache_storage_->CreateCacheHandle(this);
 }
 
+int64_t CacheStorageCache::PaddedCacheSize() const {
+  DCHECK_NE(BACKEND_UNINITIALIZED, backend_state_);
+  if (cache_size_ == CacheStorage::kSizeUnknown ||
+      cache_padding_ == CacheStorage::kSizeUnknown) {
+    return CacheStorage::kSizeUnknown;
+  }
+  return cache_size_ + cache_padding_;
+}
+
 }  // namespace content