Fix crash in CSSStyleSheetResource::appendData

third_party/WebKit/Source/core/fetch/CSSStyleSheetResource.cpp

Index: third_party/WebKit/Source/core/fetch/CSSStyleSheetResource.cpp
diff --git a/third_party/WebKit/Source/core/fetch/CSSStyleSheetResource.cpp b/third_party/WebKit/Source/core/fetch/CSSStyleSheetResource.cpp
index 78ebcd9928613cb4efdb798cef7753d0910e510b..d939116b07eb0a46e8c88e78f295af43623d5464 100644
--- a/third_party/WebKit/Source/core/fetch/CSSStyleSheetResource.cpp
+++ b/third_party/WebKit/Source/core/fetch/CSSStyleSheetResource.cpp
@@ -102,6 +102,8 @@ const String CSSStyleSheetResource::sheetText(MIMETypeCheck mimeTypeCheck) const
 void CSSStyleSheetResource::appendData(const char* data, size_t length)
 {
     Resource::appendData(data, length);
+    if (!m_data)

[Nate Chapin, 2016/05/02 19:00:43]

This should only be possible when m_options.dataBufferingPolicy ==
DoNotBufferData, but it doesn't look like CSSStyleSheetResource loads ever use
DoNotBufferData.

[Charlie Harrison, 2016/05/02 19:27:56]

Ah good point.

+        return;
     if (m_didNotifyFirstData)
         return;
     ResourceClientWalker<StyleSheetResourceClient> w(m_clients);