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 3607bfd42a08531c55d05bc0075aa61e48261d0c..f546a9be8d5a7da724d2a0a1eb5ae60a8449fe9a 100644
--- a/net/url_request/sdch_dictionary_fetcher.cc
+++ b/net/url_request/sdch_dictionary_fetcher.cc
@@ -15,6 +15,7 @@
 #include "net/base/load_flags.h"
 #include "net/base/net_log.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"
@@ -43,64 +44,40 @@ int GetReadResult(int bytes_read, const URLRequest* request) {
 
 }  // namespace
 
-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_SEND_REQUEST;
+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();
 }
 
@@ -115,6 +92,23 @@ void SdchDictionaryFetcher::OnResponseStarted(URLRequest* request) {
   DCHECK_EQ(next_state_, STATE_SEND_REQUEST_COMPLETE);
   DCHECK(!in_loop_);
 
+  // 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();

[mmenke, 2015/02/12 20:40:35]

I think this is ugly...I have some other suggestions about what to do in this
case elsewhere, but I suggest for this block:

int result = request->status().error();
if (result == OK && response_headers) {
  ...
  if (validation_type != VALIDATION_NONE) {
    // There's a cache entry, but it's expired.  Treat it as a failed request.
    result = ERR_FAILED;
  }
}

DoLoop(result);


The advantage here is that you go through the exact same flow as for requests
that are actually failed, which I think reduces complexity a bit.

[Elly Fong-Jones, 2015/02/13 23:35:00]

Done.

+      return;
+    }
+  }
+
   DoLoop(request->status().error());
 }
 
@@ -133,6 +127,76 @@ void SdchDictionaryFetcher::OnReadCompleted(URLRequest* request,
   DoLoop(GetReadResult(bytes_read, current_request_.get()));
 }
 
+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(const QueuedInfo& rhs) = default;
+
+SdchDictionaryFetcher::QueuedInfo&
+SdchDictionaryFetcher::QueuedInfo::operator=(const QueuedInfo& rhs) = default;
+
+SdchDictionaryFetcher::QueuedInfo::~QueuedInfo() {
+}
+
+void SdchDictionaryFetcher::ScheduleInternal(
+    const GURL& dictionary_url,
+    bool reload,
+    const OnDictionaryFetchedCallback& callback) {
+  DCHECK(CalledOnValidThread());

[mmenke, 2015/02/12 20:40:35]

Include base/logging.h

[Elly Fong-Jones, 2015/02/13 23:35:01]

Done.

+
+  // 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_SEND_REQUEST;
+
+  // 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_SEND_REQUEST;
+  dictionary_.clear();
+
+  if (!in_loop_)

[mmenke, 2015/02/12 20:40:35]

I think this in_loop_ check is pretty ugly.

Suggest getting rid of it and moving the next_state_ = BLAH out of the method.

Then at both callsites, set the next state, and only enter the DoLoop where
needed.

Alternatively, could make this a new state (STATE_RESET_REQUEST?).  Could put it
at the start of STATE_SEND_REQUEST, and everything would work, but that seems
icky.

[Elly Fong-Jones, 2015/02/13 23:35:00]

Done.

+    DoLoop(OK);
+  return;
+}
+
 int SdchDictionaryFetcher::DoLoop(int rv) {
   DCHECK(!in_loop_);
   base::AutoReset<bool> auto_reset_in_loop(&in_loop_, true);
@@ -178,10 +242,14 @@ int SdchDictionaryFetcher::DoSendRequest(int rv) {
   next_state_ = STATE_SEND_REQUEST_COMPLETE;
 
   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));

[mmenke, 2015/02/12 20:40:35]

optional:  This is one cases where I think using a local is clearer.  i.e.

int load_flags = blah;
if (blah)
  load_flags |= blah;
current_request_->SetLoadFlags(blah);

[Elly Fong-Jones, 2015/02/13 23:35:01]

Done.

+
   buffer_ = new IOBuffer(kBufferSize);
+  current_callback_ = fetch_queue_.front().callback;

[mmenke, 2015/02/12 20:40:35]

optional:  Might be simplest just to get rid of current_callback_, and have the
invariant that the current fetch is for the object at the front of the queue. 
Either way, should document whichever is the case in the header.

[Elly Fong-Jones, 2015/02/13 23:35:01]

Unfortunately we pull it out of the queue right after this :(.

   fetch_queue_.pop();
 
   current_request_->Start();
@@ -211,10 +279,7 @@ int SdchDictionaryFetcher::DoReadBody(int rv) {
 
   // If there's been an error, abort the current request.
   if (rv != OK) {
-    current_request_.reset();
-    buffer_ = NULL;
-    next_state_ = STATE_SEND_REQUEST;
-
+    ResetRequest();
     return OK;
   }
 
@@ -255,18 +320,13 @@ int SdchDictionaryFetcher::DoReadBodyComplete(int rv) {
 int SdchDictionaryFetcher::DoCompleteRequest(int rv) {
   DCHECK(CalledOnValidThread());
 
-  // DoReadBodyComplete() only transitions to this state
-  // on success.
-  DCHECK_EQ(OK, rv);
-
-  dictionary_fetched_callback_.Run(dictionary_, current_request_->url(),
-                                   current_request_->net_log());
-  current_request_.reset();
-  buffer_ = NULL;
-  dictionary_.clear();
-
-  next_state_ = STATE_SEND_REQUEST;
+  // If the dictionary was successfully fetched, add it to the manager.
+  if (rv == OK) {
+    current_callback_.Run(dictionary_, current_request_->url(),
+                          current_request_->net_log());
+  }
 
+  ResetRequest();
   return OK;
 }