Make SDCH dictionaries persistent across browser restart.

net/url_request/sdch_dictionary_fetcher.cc

Index: net/url_request/sdch_dictionary_fetcher.cc
diff --git a/net/url_request/sdch_dictionary_fetcher.cc b/net/url_request/sdch_dictionary_fetcher.cc
index b30f78ac2bd06e0f4318d1752494171e9cfb5682..504d18acf49ea754db907a90bdb6bb5444f7bc72 100644
--- a/net/url_request/sdch_dictionary_fetcher.cc
+++ b/net/url_request/sdch_dictionary_fetcher.cc
@@ -14,6 +14,7 @@
 #include "net/base/io_buffer.h"
 #include "net/base/load_flags.h"
 #include "net/base/sdch_net_log_params.h"
+#include "net/http/http_response_headers.h"
 #include "net/url_request/url_request_context.h"
 #include "net/url_request/url_request_status.h"
 #include "net/url_request/url_request_throttler_manager.h"
@@ -26,64 +27,40 @@ const int kBufferSize = 4096;
 
 namespace net {
 
-SdchDictionaryFetcher::SdchDictionaryFetcher(
-    URLRequestContext* context,
-    const OnDictionaryFetchedCallback& callback)
+SdchDictionaryFetcher::SdchDictionaryFetcher(URLRequestContext* context)
     : next_state_(STATE_NONE),
       in_loop_(false),
       context_(context),
-      dictionary_fetched_callback_(callback),
       weak_factory_(this) {
   DCHECK(CalledOnValidThread());
   DCHECK(context);
 }
 
 SdchDictionaryFetcher::~SdchDictionaryFetcher() {
-  DCHECK(CalledOnValidThread());
 }
 
-void SdchDictionaryFetcher::Schedule(const GURL& dictionary_url) {
-  DCHECK(CalledOnValidThread());
-
-  // Avoid pushing duplicate copy onto queue. We may fetch this url again later
-  // and get a different dictionary, but there is no reason to have it in the
-  // queue twice at one time.
-  if ((!fetch_queue_.empty() && fetch_queue_.back() == dictionary_url) ||
-      attempted_load_.find(dictionary_url) != attempted_load_.end()) {
-    // TODO(rdsmith): log this error to the net log of the URLRequest
-    // initiating this fetch, once URLRequest will be passed here.
-    SdchManager::SdchErrorRecovery(
-        SDCH_DICTIONARY_PREVIOUSLY_SCHEDULED_TO_DOWNLOAD);
-    return;
-  }
-
-  attempted_load_.insert(dictionary_url);
-  fetch_queue_.push(dictionary_url);
-
-  // If the loop is already processing, it'll pick up the above in the
-  // normal course of events.
-  if (next_state_ != STATE_NONE)
-    return;
-
-  next_state_ = STATE_IDLE;
+void SdchDictionaryFetcher::Schedule(
+    const GURL& dictionary_url,
+    const OnDictionaryFetchedCallback& callback) {
+  ScheduleInternal(dictionary_url, false, callback);
+}
 
-  // There are no callbacks to user code from the dictionary fetcher,
-  // and Schedule() is only called from user code, so this call to DoLoop()
-  // does not require an |if (in_loop_) return;| guard.
-  DoLoop(OK);
+void SdchDictionaryFetcher::ScheduleReload(
+    const GURL& dictionary_url,
+    const OnDictionaryFetchedCallback& callback) {
+  ScheduleInternal(dictionary_url, true, callback);
 }
 
 void SdchDictionaryFetcher::Cancel() {
   DCHECK(CalledOnValidThread());
 
   next_state_ = STATE_NONE;
+  current_request_.reset();
+  buffer_ = nullptr;
+  current_callback_.Reset();
 
-  while (!fetch_queue_.empty())
-    fetch_queue_.pop();
   attempted_load_.clear();
   weak_factory_.InvalidateWeakPtrs();
-  current_request_.reset(NULL);
-  buffer_ = NULL;
   dictionary_.clear();
 }
 
@@ -97,6 +74,23 @@ void SdchDictionaryFetcher::OnResponseStarted(URLRequest* request) {
   DCHECK_EQ(request, current_request_.get());
   DCHECK_EQ(next_state_, STATE_REQUEST_STARTED);
 
+  // Confirm that the response isn't a stale read from the cache (as
+  // may happen in the reload case).  If the response was not retrieved over
+  // HTTP, it is presumed to be fresh.
+  HttpResponseHeaders* response_headers = request->response_headers();
+  if (response_headers) {
+    ValidationType validation_type = response_headers->RequiresValidation(
+        request->response_info().request_time,
+        request->response_info().response_time, base::Time::Now());
+    // TODO(rdsmith): Maybe handle VALIDATION_ASYNCHRONOUS by queueing
+    // a non-reload request for the dictionary.
+    if (validation_type != VALIDATION_NONE) {
+      // Stale entry; drop it on the floor.
+      ResetRequest();
+      return;
+    }
+  }
+
   // The response has started, so the stream can be read from.
   next_state_ = STATE_REQUEST_READING;
 
@@ -135,6 +129,71 @@ void SdchDictionaryFetcher::OnReadCompleted(URLRequest* request,
   DoLoop(request->status().error());
 }
 
+SdchDictionaryFetcher::QueuedInfo::QueuedInfo()
+    : download_only_from_cache(false) {
+}
+
+SdchDictionaryFetcher::QueuedInfo::QueuedInfo(
+    const GURL& url,
+    bool download_only_from_cache,
+    const OnDictionaryFetchedCallback& callback)
+    : url(url),
+      download_only_from_cache(download_only_from_cache),
+      callback(callback) {
+}
+
+SdchDictionaryFetcher::QueuedInfo::~QueuedInfo() {
+}
+
+void SdchDictionaryFetcher::ScheduleInternal(
+    const GURL& dictionary_url,
+    bool reload,
+    const OnDictionaryFetchedCallback& callback) {
+  DCHECK(CalledOnValidThread());
+
+  // Avoid pushing duplicate copy onto queue. We may fetch this url again later
+  // and get a different dictionary, but there is no reason to have it in the
+  // queue twice at one time.
+  if ((!fetch_queue_.empty() && fetch_queue_.back().url == dictionary_url) ||
+      attempted_load_.find(dictionary_url) != attempted_load_.end()) {
+    // TODO(rdsmith): Log this error to the net log.  In the case of a
+    // normal fetch, this can be through the URLRequest
+    // initiating this fetch (once the URLRequest is passed to the fetcher);
+    // in the case of a reload, it's more complicated.
+    SdchManager::SdchErrorRecovery(
+        SDCH_DICTIONARY_PREVIOUSLY_SCHEDULED_TO_DOWNLOAD);
+    return;
+  }
+
+  if (!reload)
+    attempted_load_.insert(dictionary_url);
+  fetch_queue_.push(QueuedInfo(dictionary_url, reload, callback));
+
+  // If the loop is already processing, it'll pick up the above in the
+  // normal course of events.
+  if (next_state_ != STATE_NONE)
+    return;
+
+  next_state_ = STATE_IDLE;
+
+  // There are no callbacks to user code from the dictionary fetcher,
+  // and Schedule() is only called from user code, so this call to DoLoop()
+  // does not require an |if (in_loop_) return;| guard.
+  DoLoop(OK);
+}
+
+void SdchDictionaryFetcher::ResetRequest() {
+  current_request_.reset();
+  buffer_ = nullptr;
+  current_callback_.Reset();
+  next_state_ = STATE_IDLE;
+  dictionary_.clear();
+
+  if (!in_loop_)
+    DoLoop(OK);
+  return;
+}
+
 int SdchDictionaryFetcher::DoLoop(int rv) {
   DCHECK(!in_loop_);
   base::AutoReset<bool> auto_reset_in_loop(&in_loop_, true);
@@ -175,10 +234,14 @@ int SdchDictionaryFetcher::DoDispatchRequest(int rv) {
   }
 
   current_request_ =
-      context_->CreateRequest(fetch_queue_.front(), IDLE, this, NULL);
-  current_request_->SetLoadFlags(LOAD_DO_NOT_SEND_COOKIES |
-                                 LOAD_DO_NOT_SAVE_COOKIES);
+      context_->CreateRequest(fetch_queue_.front().url, IDLE, this, NULL);
+  current_request_->SetLoadFlags(
+      LOAD_DO_NOT_SEND_COOKIES | LOAD_DO_NOT_SAVE_COOKIES |
+      (fetch_queue_.front().download_only_from_cache ? LOAD_ONLY_FROM_CACHE
+                                                     : 0));
+
   buffer_ = new IOBuffer(kBufferSize);
+  current_callback_ = fetch_queue_.front().callback;
   fetch_queue_.pop();
 
   next_state_ = STATE_REQUEST_STARTED;
@@ -207,10 +270,7 @@ int SdchDictionaryFetcher::DoRead(int rv) {
 
   // If there's been an error, abort the current request.
   if (rv != OK) {
-    current_request_.reset();
-    buffer_ = NULL;
-    next_state_ = STATE_IDLE;
-
+    ResetRequest();
     return OK;
   }
 
@@ -248,16 +308,11 @@ int SdchDictionaryFetcher::DoCompleteRequest(int rv) {
 
   // If the dictionary was successfully fetched, add it to the manager.
   if (rv == OK) {
-    dictionary_fetched_callback_.Run(dictionary_, current_request_->url(),
-                                     current_request_->net_log());
+    current_callback_.Run(dictionary_, current_request_->url(),
+                          current_request_->net_log());
   }
 
-  current_request_.reset();
-  buffer_ = NULL;
-  dictionary_.clear();
-
-  next_state_ = STATE_IDLE;
-
+  ResetRequest();
   return OK;
 }