Cleanup comparison with NULL for DCHECK.

Substitutes smart_pointer.get() == NULL with !smart_pointer in DCHECKs.

BUG=NONE

Review-Url: https://codereview.chromium.org/2030693003
Cr-Commit-Position: refs/heads/master@{#399334}
diff --git a/net/websockets/websocket_basic_stream.cc b/net/websockets/websocket_basic_stream.cc
index 1c57584..e13e1eb 100644
--- a/net/websockets/websocket_basic_stream.cc
+++ b/net/websockets/websocket_basic_stream.cc
@@ -97,7 +97,7 @@
     // large.
     scoped_refptr<GrowableIOBuffer> buffered_data;
     buffered_data.swap(http_read_buffer_);
-    DCHECK(http_read_buffer_.get() == NULL);
+    DCHECK(!http_read_buffer_);
     std::vector<std::unique_ptr<WebSocketFrameChunk>> frame_chunks;
     if (!parser_.Decode(buffered_data->StartOfBuffer(),
                         buffered_data->offset(),