Implementation of subresource integrity attribute for style sheets.

Source/core/html/HTMLLinkElement.cpp

Index: Source/core/html/HTMLLinkElement.cpp
diff --git a/Source/core/html/HTMLLinkElement.cpp b/Source/core/html/HTMLLinkElement.cpp
index 725217d564185e6dce1e2d0ebecd2a23a2d44b73..93bc16b9007e9dd898acf7c74176ffd66054762e 100644
--- a/Source/core/html/HTMLLinkElement.cpp
+++ b/Source/core/html/HTMLLinkElement.cpp
@@ -42,6 +42,7 @@
 #include "core/fetch/ResourceFetcher.h"
 #include "core/frame/FrameView.h"
 #include "core/frame/LocalFrame.h"
+#include "core/frame/SubresourceIntegrity.h"
 #include "core/frame/csp/ContentSecurityPolicy.h"
 #include "core/html/LinkManifest.h"
 #include "core/html/imports/LinkImport.h"
@@ -501,8 +502,14 @@ void LinkStyle::setCSSStyleSheet(const String& href, const KURL& baseURL, const
     if (!m_owner->inDocument()) {
         ASSERT(!m_sheet);
         return;
+    }
 
+    if (!SubresourceIntegrity::CheckSubresourceIntegrity(*m_owner, cachedStyleSheet->sheetText(), KURL(KURL(), href))) {
+        m_loading = false;
+        removePendingSheet();
+        return;
     }
+
     // Completing the sheet load may cause scripts to execute.
     RefPtrWillBeRawPtr<Node> protector(m_owner.get());
 
@@ -527,6 +534,7 @@ void LinkStyle::setCSSStyleSheet(const String& href, const KURL& baseURL, const
 
     if (m_sheet)
         clearSheet();
+
     m_sheet = CSSStyleSheet::create(styleSheet, m_owner);
     m_sheet->setMediaQueries(MediaQuerySet::create(m_owner->media()));
     m_sheet->setTitle(m_owner->title());