Bug 734062 - stale image in the image cache when an updated version is fetched into HTML5 offline cache in background, r=joedrew

image/src/imgLoader.cpp

@@ -2112,7 +2112,7 @@ NS_IMETHODIMP imgCacheValidator::OnStartRequest(nsIRequest *aRequest, nsISupport
   // we have to do is tell them to notify their listeners.
   nsCOMPtr<nsICachingChannel> cacheChan(do_QueryInterface(aRequest));
   nsCOMPtr<nsIChannel> channel(do_QueryInterface(aRequest));
-  if (cacheChan && channel) {
+  if (cacheChan && channel && !mRequest->CacheChanged(aRequest)) {
     bool isFromCache = false;
     cacheChan->IsFromCache(&isFromCache);
 

image/src/imgRequest.cpp

@@ -30,6 +30,8 @@
 #include "nsIInputStream.h"
 #include "nsIMultiPartChannel.h"
 #include "nsIHttpChannel.h"
+#include "nsIApplicationCache.h"
+#include "nsIApplicationCacheChannel.h"
 
 #include "nsIComponentManager.h"
 #include "nsIInterfaceRequestorUtils.h"
@@ -440,6 +442,67 @@ void imgRequest::SetCacheValidation(imgCacheEntry* aCacheEntry, nsIRequest* aReq
   }
 }
 
+namespace { // anon
+
+already_AddRefed<nsIApplicationCache>
+GetApplicationCache(nsIRequest* aRequest)
+{
+  nsresult rv;
+
+  nsCOMPtr<nsIApplicationCacheChannel> appCacheChan = do_QueryInterface(aRequest);
+  if (!appCacheChan) {
+    return nullptr;
+  }
+
+  bool fromAppCache;
+  rv = appCacheChan->GetLoadedFromApplicationCache(&fromAppCache);
+  NS_ENSURE_SUCCESS(rv, nullptr);
+
+  if (!fromAppCache) {
+    return nullptr;
+  }
+
+  nsCOMPtr<nsIApplicationCache> appCache;
+  rv = appCacheChan->GetApplicationCache(getter_AddRefs(appCache));
+  NS_ENSURE_SUCCESS(rv, nullptr);
+
+  return appCache.forget();
+}
+
+} // anon
+
+bool
+imgRequest::CacheChanged(nsIRequest* aNewRequest)
+{
+  nsresult rv;
+
+  nsCOMPtr<nsIApplicationCache> newAppCache = GetApplicationCache(aNewRequest);
+  NS_ENSURE_SUCCESS(rv, true); // cannot determine, play safely
+
+  // Application cache not involved at all or the same app cache involved
+  // in both of the loads (original and new).
+  if (newAppCache == mApplicationCache)
+    return false;
+
+  // In a rare case it may happen that two objects still refer
+  // the same application cache version.
+  if (newAppCache && mApplicationCache) {
+    nsAutoCString oldAppCacheClientId, newAppCacheClientId;
+    rv = mApplicationCache->GetClientID(oldAppCacheClientId);
+    NS_ENSURE_SUCCESS(rv, true);
+    rv = newAppCache->GetClientID(newAppCacheClientId);
+    NS_ENSURE_SUCCESS(rv, true);
+
+    if (oldAppCacheClientId == newAppCacheClientId)
+      return false;
+  }
+
+  // When we get here, app caches differ or app cache is involved
+  // just in one of the loads what we also consider as a change
+  // in a loading cache.
+  return true;
+}
+
 nsresult
 imgRequest::LockImage()
 {
@@ -547,6 +610,8 @@ NS_IMETHODIMP imgRequest::OnStartRequest(nsIRequest *aRequest, nsISupports *ctxt
 
   SetCacheValidation(mCacheEntry, aRequest);
 
+  mApplicationCache = GetApplicationCache(aRequest);
+
   // Shouldn't we be dead already if this gets hit?  Probably multipart/x-mixed-replace...
   if (GetStatusTracker().ConsumerCount() == 0) {
     this->Cancel(NS_IMAGELIB_ERROR_FAILURE);

image/src/imgRequest.h

@@ -16,6 +16,7 @@
 #include "nsIURI.h"
 #include "nsIPrincipal.h"
 #include "nsITimedChannel.h"
+#include "nsIApplicationCache.h"
 
 #include "nsCategoryCache.h"
 #include "nsCOMPtr.h"
@@ -91,6 +92,12 @@ public:
   // wins.
   static void SetCacheValidation(imgCacheEntry* aEntry, nsIRequest* aRequest);
 
+  // Check if application cache of the original load is different from
+  // application cache of the new load.  Also lack of application cache
+  // on one of the loads is considered a change of a loading cache since
+  // HTTP cache may contain a different data then app cache.
+  bool CacheChanged(nsIRequest* aNewRequest);
+
   bool GetMultipart() const { return mIsMultiPartChannel; }
 
   // The CORS mode for which we loaded this image.
@@ -200,6 +207,7 @@ private:
   nsCOMPtr<nsISupports> mSecurityInfo;
   nsCOMPtr<nsIChannel> mChannel;
   nsCOMPtr<nsIInterfaceRequestor> mPrevChannelSink;
+  nsCOMPtr<nsIApplicationCache> mApplicationCache;
 
   nsCOMPtr<nsITimedChannel> mTimedChannel;