Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/platform/network/HTTPRequest.cpp

Index: Source/platform/network/HTTPRequest.cpp
diff --git a/Source/platform/network/HTTPRequest.cpp b/Source/platform/network/HTTPRequest.cpp
index d003572167064d24004c423c9ac5d3874c722f1f..cd1694e56032c0760a6fbd8be3c5904314ce3563 100644
--- a/Source/platform/network/HTTPRequest.cpp
+++ b/Source/platform/network/HTTPRequest.cpp
@@ -34,7 +34,7 @@ PassRefPtr<HTTPRequest> HTTPRequest::parseHTTPRequestFromBuffer(const char* data
 {
     if (!length) {
         failureReason = "No data to parse.";
-        return 0;
+        return nullptr;
     }
 
     // Request we will be building.
@@ -47,14 +47,14 @@ PassRefPtr<HTTPRequest> HTTPRequest::parseHTTPRequestFromBuffer(const char* data
     // 1. Parse Method + URL.
     size_t requestLineLength = request->parseRequestLine(pos, remainingLength, failureReason);
     if (!requestLineLength)
-        return 0;
+        return nullptr;
     pos += requestLineLength;
     remainingLength -= requestLineLength;
 
     // 2. Parse HTTP Headers.
     size_t headersLength = request->parseHeaders(pos, remainingLength, failureReason);
     if (!headersLength)
-        return 0;
+        return nullptr;
     pos += headersLength;
     remainingLength -= headersLength;