Refactor MIME type related methods in XHR for readability

- Give more descriptive names to MIME type related methods
- Split responseMIMEType() into one without fallback to text/xml and one
  with it as this fallback is requird only a few places
- Add some FIXMEs to address issues found during this refactoring later

BUG=none

Review URL: https://codereview.chromium.org/450103003

git-svn-id: svn://svn.chromium.org/blink/trunk@179950 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/core/xml/XMLHttpRequest.cpp

@@ -190,7 +190,7 @@ ScriptString XMLHttpRequest::responseJSONSource()
 
 void XMLHttpRequest::initResponseDocument()
 {
-    AtomicString mimeType = responseMIMEType();
+    AtomicString mimeType = finalResponseMIMETypeWithFallback();
     bool isHTML = equalIgnoringCase(mimeType, "text/html");
 
     // The W3C spec requires the final MIME type to be some valid XML type, or text/html.
@@ -259,7 +259,10 @@ Blob* XMLHttpRequest::responseBlob()
         // empty one.
         if (!filePath.isEmpty() && m_downloadedBlobLength) {
             blobData->appendFile(filePath);
-            blobData->setContentType(responseMIMEType()); // responseMIMEType defaults to text/xml which may be incorrect.
+            // FIXME: finalResponseMIMETypeWithFallback() defaults to text/xml
+            // which may be incorrect. Replace it with finalResponseMIMEType()
+            // after compatibility investigation.
+            blobData->setContentType(finalResponseMIMETypeWithFallback());
         }
         m_responseBlob = Blob::create(BlobDataHandle::create(blobData.release(), m_downloadedBlobLength));
     }
@@ -879,7 +882,7 @@ void XMLHttpRequest::clearVariablesForLoading()
 {
     m_decoder.clear();
 
-    m_responseEncoding = String();
+    m_finalResponseCharset = String();
 }
 
 bool XMLHttpRequest::internalAbort()
@@ -1030,6 +1033,9 @@ void XMLHttpRequest::handleRequestError(ExceptionCode exceptionCode, const Atomi
 
 void XMLHttpRequest::overrideMimeType(const AtomicString& override)
 {
+    // FIXME: This method must throw an InvalidStateError exception when the
+    // XHR is in the LOADING or DONE state. http://crbug.com/402375
+
     m_mimeTypeOverride = override;
 }
 
@@ -1126,24 +1132,32 @@ const AtomicString& XMLHttpRequest::getResponseHeader(const AtomicString& name)
     return m_response.httpHeaderField(name);
 }
 
-AtomicString XMLHttpRequest::responseMIMEType() const
+AtomicString XMLHttpRequest::finalResponseMIMEType() const
 {
-    AtomicString mimeType = extractMIMETypeFromMediaType(m_mimeTypeOverride);
-    if (mimeType.isEmpty()) {
-        if (m_response.isHTTP())
-            mimeType = extractMIMETypeFromMediaType(m_response.httpHeaderField("Content-Type"));
-        else
-            mimeType = m_response.mimeType();
-    }
-    if (mimeType.isEmpty())
-        mimeType = AtomicString("text/xml", AtomicString::ConstructFromLiteral);
+    AtomicString overriddenType = extractMIMETypeFromMediaType(m_mimeTypeOverride);
+    if (!overriddenType.isEmpty())
+        return overriddenType;
+
+    if (m_response.isHTTP())
+        return extractMIMETypeFromMediaType(m_response.httpHeaderField("Content-Type"));
+
+    return m_response.mimeType();
+}
+
+AtomicString XMLHttpRequest::finalResponseMIMETypeWithFallback() const
+{
+    AtomicString finalType = finalResponseMIMEType();
+    if (!finalType.isEmpty())
+        return finalType;
 
-    return mimeType;
+    // FIXME: This fallback is not specified in the final MIME type algorithm
+    // of the XHR spec. Move this to more appropriate place.
+    return AtomicString("text/xml", AtomicString::ConstructFromLiteral);
 }
 
 bool XMLHttpRequest::responseIsXML() const
 {
-    return DOMImplementation::isXMLMIMEType(responseMIMEType());
+    return DOMImplementation::isXMLMIMEType(finalResponseMIMETypeWithFallback());
 }
 
 int XMLHttpRequest::status() const
@@ -1250,11 +1264,11 @@ void XMLHttpRequest::didReceiveResponse(unsigned long identifier, const Resource
     m_response = response;
     if (!m_mimeTypeOverride.isEmpty()) {
         m_response.setHTTPHeaderField("Content-Type", m_mimeTypeOverride);
-        m_responseEncoding = extractCharsetFromMediaType(m_mimeTypeOverride);
+        m_finalResponseCharset = extractCharsetFromMediaType(m_mimeTypeOverride);
     }
 
-    if (m_responseEncoding.isEmpty())
-        m_responseEncoding = response.textEncodingName();
+    if (m_finalResponseCharset.isEmpty())
+        m_finalResponseCharset = response.textEncodingName();
 }
 
 PassOwnPtr<TextResourceDecoder> XMLHttpRequest::createDecoder() const
@@ -1262,8 +1276,8 @@ PassOwnPtr<TextResourceDecoder> XMLHttpRequest::createDecoder() const
     if (m_responseTypeCode == ResponseTypeJSON)
         return TextResourceDecoder::create("application/json", "UTF-8");
 
-    if (!m_responseEncoding.isEmpty())
-        return TextResourceDecoder::create("text/plain", m_responseEncoding);
+    if (!m_finalResponseCharset.isEmpty())
+        return TextResourceDecoder::create("text/plain", m_finalResponseCharset);
 
     // allow TextResourceDecoder to look inside the m_response if it's XML or HTML
     if (responseIsXML()) {
@@ -1276,7 +1290,7 @@ PassOwnPtr<TextResourceDecoder> XMLHttpRequest::createDecoder() const
         return decoder.release();
     }
 
-    if (equalIgnoringCase(responseMIMEType(), "text/html"))
+    if (equalIgnoringCase(finalResponseMIMEType(), "text/html"))
         return TextResourceDecoder::create("text/html", "UTF-8");
 
     return TextResourceDecoder::create("text/plain", "UTF-8");
@@ -1311,7 +1325,7 @@ void XMLHttpRequest::didReceiveData(const char* data, int len)
         m_binaryResponseBuilder->append(data, len);
     } else if (m_responseTypeCode == ResponseTypeLegacyStream) {
         if (!m_responseStream)
-            m_responseStream = Stream::create(executionContext(), responseMIMEType());
+            m_responseStream = Stream::create(executionContext(), finalResponseMIMEType());
         m_responseStream->addData(data, len);
     }
 

third_party/WebKit/Source/core/xml/XMLHttpRequest.h

@@ -160,7 +160,18 @@ private:
     virtual void didFail(const ResourceError&) OVERRIDE;
     virtual void didFailRedirectCheck() OVERRIDE;
 
-    AtomicString responseMIMEType() const;
+    // Returns the MIME type part of m_mimeTypeOverride if present and
+    // successfully parsed, or returns one of the "Content-Type" header value
+    // of the received response.
+    //
+    // This method is named after the term "final MIME type" defined in the
+    // spec but doesn't convert the result to ASCII lowercase as specified in
+    // the spec. Must be lowered later or compared using case insensitive
+    // comparison functions if required.
+    AtomicString finalResponseMIMEType() const;
+    // The same as finalResponseMIMEType() but fallbacks to "text/xml" if
+    // finalResponseMIMEType() returns an empty string.
+    AtomicString finalResponseMIMETypeWithFallback() const;
     bool responseIsXML() const;
 
     PassOwnPtr<TextResourceDecoder> createDecoder() const;
@@ -212,6 +223,8 @@ private:
     KURL m_url;
     AtomicString m_method;
     HTTPHeaderMap m_requestHeaders;
+    // Not converted to ASCII lowercase. Must be lowered later or compared
+    // using case insensitive comparison functions if needed.
     AtomicString m_mimeTypeOverride;
     unsigned long m_timeoutMilliseconds;
     RefPtrWillBeMember<Blob> m_responseBlob;
@@ -221,7 +234,7 @@ private:
     State m_state;
 
     ResourceResponse m_response;
-    String m_responseEncoding;
+    String m_finalResponseCharset;
 
     OwnPtr<TextResourceDecoder> m_decoder;