bug 792438 part 3: a kill switch r=honzab

modules/libpref/src/init/all.js

@@ -914,6 +914,10 @@ pref("network.http.connection-timeout", 90);
 // when starting a new speculative connection.
 pref("network.http.speculative-parallel-limit", 6);
 
+// Whether or not to block requests for non head js/css items (e.g. media)
+// while those elements load.
+pref("network.http.rendering-critical-requests-prioritization", true);
+
 // Disable IPv6 for backup connections to workaround problems about broken
 // IPv6 connectivity.
 pref("network.http.fast-fallback-to-IPv4", true);

netwerk/protocol/http/nsHttpChannel.cpp

@@ -4445,10 +4445,12 @@ nsHttpChannel::BeginConnect()
         (BYPASS_LOCAL_CACHE(mLoadFlags)))
         mCaps |= NS_HTTP_REFRESH_DNS;
 
-    if (mLoadAsBlocking)
-        mCaps |= NS_HTTP_LOAD_AS_BLOCKING;
-    if (mLoadUnblocked)
-        mCaps |= NS_HTTP_LOAD_UNBLOCKED;
+    if (gHttpHandler->CritialRequestPrioritization()) {
+        if (mLoadAsBlocking)
+            mCaps |= NS_HTTP_LOAD_AS_BLOCKING;
+        if (mLoadUnblocked)
+            mCaps |= NS_HTTP_LOAD_UNBLOCKED;
+    }
 
     // Force-Reload should reset the persistent connection pool for this host
     if (mLoadFlags & LOAD_FRESH_CONNECTION) {

netwerk/protocol/http/nsHttpHandler.cpp

@@ -179,6 +179,7 @@ nsHttpHandler::nsHttpHandler()
     , mSpdyPingTimeout(PR_SecondsToInterval(8))
     , mConnectTimeout(90000)
     , mParallelSpeculativeConnectLimit(6)
+    , mCritialRequestPrioritization(true)
 {
 #if defined(PR_LOGGING)
     gHttpLog = PR_NewLogModule("nsHttp");
@@ -1147,6 +1148,14 @@ nsHttpHandler::PrefsChanged(nsIPrefBranch *prefs, const char *pref)
             mParallelSpeculativeConnectLimit = (uint32_t) clamped(val, 0, 1024);
     }
 
+    // Whether or not to block requests for non head js/css items (e.g. media)
+    // while those elements load.
+    if (PREF_CHANGED(HTTP_PREF("rendering-critical-requests-prioritization"))) {
+        rv = prefs->GetBoolPref(HTTP_PREF("rendering-critical-requests-prioritization"), &cVar);
+        if (NS_SUCCEEDED(rv))
+            mCritialRequestPrioritization = cVar;
+    }
+
     // on transition of network.http.diagnostics to true print
     // a bunch of information to the console
     if (pref && PREF_CHANGED(HTTP_PREF("diagnostics"))) {

netwerk/protocol/http/nsHttpHandler.h

@@ -98,6 +98,7 @@ public:
     PRIntervalTime SpdyPingTimeout() { return mSpdyPingTimeout; }
     uint32_t       ConnectTimeout()  { return mConnectTimeout; }
     uint32_t       ParallelSpeculativeConnectLimit() { return mParallelSpeculativeConnectLimit; }
+    bool           CritialRequestPrioritization() { return mCritialRequestPrioritization; }
 
     bool           PromptTempRedirect()      { return mPromptTempRedirect; }
 
@@ -400,6 +401,10 @@ private:
     // The maximum number of current global half open sockets allowable
     // when starting a new speculative connection.
     uint32_t       mParallelSpeculativeConnectLimit;
+
+    // Whether or not to block requests for non head js/css items (e.g. media)
+    // while those elements load.
+    bool           mCritialRequestPrioritization;
 };
 
 //-----------------------------------------------------------------------------