Revert "CSS: Drop the quirks-mode exception for CSS MIME types."

Source/core/fetch/CSSStyleSheetResource.cpp

Index: Source/core/fetch/CSSStyleSheetResource.cpp
diff --git a/Source/core/fetch/CSSStyleSheetResource.cpp b/Source/core/fetch/CSSStyleSheetResource.cpp
index 7281e1ead5ba6d27217131cb60f303d6d48f0d43..869d7ca543715dce7f4a7c78d1f82958ea7da477 100644
--- a/Source/core/fetch/CSSStyleSheetResource.cpp
+++ b/Source/core/fetch/CSSStyleSheetResource.cpp
@@ -77,11 +77,11 @@ void CSSStyleSheetResource::didAddClient(ResourceClient* c)
         static_cast<StyleSheetResourceClient*>(c)->setCSSStyleSheet(m_resourceRequest.url(), m_response.url(), encoding(), this);
 }
 
-const String CSSStyleSheetResource::sheetText(bool* hasValidMIMEType) const
+const String CSSStyleSheetResource::sheetText(bool enforceMIMEType, bool* hasValidMIMEType) const
 {
     ASSERT(!isPurgeable());
 
-    if (!m_data || m_data->isEmpty() || !canUseSheet(hasValidMIMEType))
+    if (!m_data || m_data->isEmpty() || !canUseSheet(enforceMIMEType, hasValidMIMEType))
         return String();
 
     if (!m_decodedSheetText.isNull())
@@ -125,11 +125,14 @@ void CSSStyleSheetResource::destroyDecodedDataIfPossible()
     setDecodedSize(0);
 }
 
-bool CSSStyleSheetResource::canUseSheet(bool* hasValidMIMEType) const
+bool CSSStyleSheetResource::canUseSheet(bool enforceMIMEType, bool* hasValidMIMEType) const
 {
     if (errorOccurred())
         return false;
 
+    if (!enforceMIMEType && !hasValidMIMEType)
+        return true;
+
     // This check exactly matches Firefox. Note that we grab the Content-Type
     // header directly because we want to see what the value is BEFORE content
     // sniffing. Firefox does this by setting a "type hint" on the channel.
@@ -140,6 +143,8 @@ bool CSSStyleSheetResource::canUseSheet(bool* hasValidMIMEType) const
     bool typeOK = mimeType().isEmpty() || equalIgnoringCase(mimeType(), "text/css") || equalIgnoringCase(mimeType(), "application/x-unknown-content-type");
     if (hasValidMIMEType)
         *hasValidMIMEType = typeOK;
+    if (!enforceMIMEType)
+        return true;
     return typeOK;
 }