--- a/dom/base/nsObjectLoadingContent.cpp
+++ b/dom/base/nsObjectLoadingContent.cpp
@@ -658,17 +658,17 @@ nsObjectLoadingContent::nsObjectLoadingC
   : mType(eType_Loading)
   , mFallbackType(eFallbackAlternate)
   , mRunID(0)
   , mHasRunID(false)
   , mChannelLoaded(false)
   , mInstantiating(false)
   , mNetworkCreated(true)
   , mActivated(false)
-  , mContentBlockingDisabled(false)
+  , mContentBlockingEnabled(false)
   , mIsStopping(false)
   , mIsLoading(false)
   , mScriptRequested(false)
   , mRewrittenYoutubeEmbed(false)
   , mPreferFallback(false)
   , mPreferFallbackKnown(false) {}
 
 nsObjectLoadingContent::~nsObjectLoadingContent()
@@ -1053,36 +1053,36 @@ nsObjectLoadingContent::OnStartRequest(n
   NS_ASSERTION(!mChannelLoaded, "mChannelLoaded set already?");
   NS_ASSERTION(!mFinalListener, "mFinalListener exists already?");
 
   mChannelLoaded = true;
 
   nsCOMPtr<nsIChannel> chan(do_QueryInterface(aRequest));
   NS_ASSERTION(chan, "Why is our request not a channel?");
 
-  nsresult status;
+  nsresult status = NS_OK;
   bool success = IsSuccessfulRequest(aRequest, &status);
 
   if (status == NS_ERROR_BLOCKED_URI) {
     nsCOMPtr<nsIConsoleService> console(
       do_GetService("@mozilla.org/consoleservice;1"));
     if (console) {
       nsCOMPtr<nsIURI> uri;
       chan->GetURI(getter_AddRefs(uri));
       nsString message = NS_LITERAL_STRING("Blocking ") +
         NS_ConvertASCIItoUTF16(uri->GetSpecOrDefault().get()) +
         NS_LITERAL_STRING(" since it was found on an internal Firefox blocklist.");
       console->LogStringMessage(message.get());
     }
     Telemetry::Accumulate(Telemetry::PLUGIN_BLOCKED_FOR_STABILITY, 1);
+    mContentBlockingEnabled = true;
     return NS_ERROR_FAILURE;
   } else if (status == NS_ERROR_TRACKING_URI) {
+    mContentBlockingEnabled = true;
     return NS_ERROR_FAILURE;
-  } else {
-    mContentBlockingDisabled = true;
   }
 
   if (!success) {
     LOG(("OBJLC [%p]: OnStartRequest: Request failed\n", this));
     // If the request fails, we still call LoadObject() to handle fallback
     // content and notifying of failure. (mChannelLoaded && !mChannel) indicates
     // the bad state.
     mChannel = nullptr;
@@ -3219,42 +3219,53 @@ nsObjectLoadingContent::GetRunID(SystemC
     return 0;
   }
   return mRunID;
 }
 
 static bool sPrefsInitialized;
 static uint32_t sSessionTimeoutMinutes;
 static uint32_t sPersistentTimeoutDays;
+static bool sBlockURIs;
+
+static void initializeObjectLoadingContentPrefs()
+{
+  if (!sPrefsInitialized) {
+    Preferences::AddUintVarCache(&sSessionTimeoutMinutes,
+                                 "plugin.sessionPermissionNow.intervalInMinutes", 60);
+    Preferences::AddUintVarCache(&sPersistentTimeoutDays,
+                                 "plugin.persistentPermissionAlways.intervalInDays", 90);
+
+    Preferences::AddBoolVarCache(&sBlockURIs, kPrefBlockURIs, false);
+    sPrefsInitialized = true;
+  }
+}
 
 bool
 nsObjectLoadingContent::ShouldBlockContent()
 {
-  if (mContentBlockingDisabled || !mURI)
-    return false;
-
-  if (!IsFlashMIME(mContentType) || !Preferences::GetBool(kPrefBlockURIs)) {
-    mContentBlockingDisabled = true;
-    return false;
+ 
+  if (!sPrefsInitialized) {
+    initializeObjectLoadingContentPrefs();
   }
 
-  return true;
+  if (mContentBlockingEnabled && mURI && IsFlashMIME(mContentType) && sBlockURIs ) {
+    return true;
+  }
+
+  return false;
 }
 
 bool
 nsObjectLoadingContent::ShouldPlay(FallbackType &aReason, bool aIgnoreCurrentType)
 {
   nsresult rv;
 
   if (!sPrefsInitialized) {
-    Preferences::AddUintVarCache(&sSessionTimeoutMinutes,
-                                 "plugin.sessionPermissionNow.intervalInMinutes", 60);
-    Preferences::AddUintVarCache(&sPersistentTimeoutDays,
-                                 "plugin.persistentPermissionAlways.intervalInDays", 90);
-    sPrefsInitialized = true;
+    initializeObjectLoadingContentPrefs();
   }
 
   if (BrowserTabsRemoteAutostart()) {
     bool shouldLoadInParent = nsPluginHost::ShouldLoadTypeInParent(mContentType);
     bool inParent = XRE_IsParentProcess();
 
     if (shouldLoadInParent != inParent) {
       // Plugins need to be locked to either the parent process or the content

--- a/dom/base/nsObjectLoadingContent.h
+++ b/dom/base/nsObjectLoadingContent.h
@@ -672,17 +672,17 @@ class nsObjectLoadingContent : public ns
     // it may lose the flag.
     bool                        mNetworkCreated : 1;
 
     // Used to keep track of whether or not a plugin has been explicitly
     // activated by PlayPlugin(). (see ShouldPlay())
     bool                        mActivated : 1;
 
     // Whether content blocking is enabled or not for this object.
-    bool                        mContentBlockingDisabled : 1;
+    bool                        mContentBlockingEnabled : 1;
 
     // Protects DoStopPlugin from reentry (bug 724781).
     bool                        mIsStopping : 1;
 
     // Protects LoadObject from re-entry
     bool                        mIsLoading : 1;
 
     // For plugin stand-in types (click-to-play) tracks