Revert of [XMLHttpRequest] Stop throwing for network error in async mode

Source/core/xmlhttprequest/XMLHttpRequest.cpp

Index: Source/core/xmlhttprequest/XMLHttpRequest.cpp
diff --git a/Source/core/xmlhttprequest/XMLHttpRequest.cpp b/Source/core/xmlhttprequest/XMLHttpRequest.cpp
index ddbde836da3c55855ac4d4c45b57722839c80089..bf26832ea0d32f46357eeee81ec981c8e2ed1d08 100644
--- a/Source/core/xmlhttprequest/XMLHttpRequest.cpp
+++ b/Source/core/xmlhttprequest/XMLHttpRequest.cpp
@@ -837,34 +837,11 @@
     m_exceptionCode = exceptionState.code();
 }
 
-void XMLHttpRequest::throwForLoadFailureIfNeeded(ExceptionState& exceptionState, const String& reason)
-{
-    if (m_error && !m_exceptionCode)
-        m_exceptionCode = NetworkError;
-
-    if (!m_exceptionCode)
-        return;
-
-    String message = "Failed to load '" + m_url.elidedString() + "'";
-    if (reason.isNull()) {
-        message.append(".");
-    } else {
-        message.append(": ");
-        message.append(reason);
-    }
-
-    exceptionState.throwDOMException(m_exceptionCode, message);
-}
-
 void XMLHttpRequest::createRequest(PassRefPtr<FormData> httpBody, ExceptionState& exceptionState)
 {
     // Only GET request is supported for blob URL.
     if (m_url.protocolIs("blob") && m_method != "GET") {
-        handleNetworkError();
-
-        if (!m_async) {
-            throwForLoadFailureIfNeeded(exceptionState, "'GET' is the only method allowed for 'blob:' URLs.");
-        }
+        exceptionState.throwDOMException(NetworkError, "'GET' is the only method allowed for 'blob:' URLs.");
         return;
     }
 
@@ -939,15 +916,16 @@
         // FIXME: Maybe create() can return null for other reasons too?
         ASSERT(!m_loader);
         m_loader = ThreadableLoader::create(executionContext, this, request, options, resourceLoaderOptions);
-
-        return;
-    }
-
-    // Use count for XHR synchronous requests.
-    UseCounter::count(&executionContext, UseCounter::XMLHttpRequestSynchronous);
-    ThreadableLoader::loadResourceSynchronously(executionContext, request, *this, options, resourceLoaderOptions);
-
-    throwForLoadFailureIfNeeded(exceptionState, String());
+    } else {
+        // Use count for XHR synchronous requests.
+        UseCounter::count(&executionContext, UseCounter::XMLHttpRequestSynchronous);
+        ThreadableLoader::loadResourceSynchronously(executionContext, request, *this, options, resourceLoaderOptions);
+    }
+
+    if (!m_exceptionCode && m_error)
+        m_exceptionCode = NetworkError;
+    if (m_exceptionCode)
+        exceptionState.throwDOMException(m_exceptionCode, "Failed to load '" + m_url.elidedString() + "'.");
 }
 
 void XMLHttpRequest::abort()