Bug 235853: don't freeze the UI when resolving DNS for PAC, by using deferred resolution if we would otherwise block on DNS. r+madskills=biesi, a-b5=mconnor

netwerk/base/src/nsIOService.cpp

@@ -550,7 +550,17 @@ nsIOService::NewChannelFromURI(nsIURI *aURI, nsIChannel **result)
                 NS_WARNING("failed to get protocol proxy service");
         }
         if (mProxyService) {
-            rv = mProxyService->Resolve(aURI, 0, getter_AddRefs(pi));
+            PRUint32 flags = 0;
+            if (scheme.EqualsLiteral("http") || scheme.EqualsLiteral("https"))
+                flags = nsIProtocolProxyService::RESOLVE_NON_BLOCKING;
+            rv = mProxyService->Resolve(aURI, flags, getter_AddRefs(pi));
+            if (rv == NS_BASE_STREAM_WOULD_BLOCK) {
+                // Use an UNKNOWN proxy to defer resolution and avoid blocking.
+                rv = mProxyService->NewProxyInfo(NS_LITERAL_CSTRING("unknown"),
+                                                 NS_LITERAL_CSTRING(""),
+                                                 -1, 0, 0, nsnull,
+                                                 getter_AddRefs(pi));
+            }
             if (NS_FAILED(rv))
                 pi = nsnull;
         }

netwerk/base/src/nsProtocolProxyService.cpp

@@ -923,7 +923,8 @@ nsProtocolProxyService::NewProxyInfo(const nsACString &aType,
         kProxyType_HTTP,
         kProxyType_SOCKS,
         kProxyType_SOCKS4,
-        kProxyType_DIRECT
+        kProxyType_DIRECT,
+        kProxyType_UNKNOWN
     };
 
     // resolve type; this allows us to avoid copying the type string into each