Fix LinkStyle SRI check when against 0 sized resource.

third_party/WebKit/Source/core/html/HTMLLinkElement.cpp

Index: third_party/WebKit/Source/core/html/HTMLLinkElement.cpp
diff --git a/third_party/WebKit/Source/core/html/HTMLLinkElement.cpp b/third_party/WebKit/Source/core/html/HTMLLinkElement.cpp
index a27a6472c4f8e94e1e0fe0c212804be928e867b0..47953c95c3ce4f91c8f7a463af8a5b5c0714060e 100644
--- a/third_party/WebKit/Source/core/html/HTMLLinkElement.cpp
+++ b/third_party/WebKit/Source/core/html/HTMLLinkElement.cpp
@@ -434,19 +434,21 @@ void LinkStyle::setCSSStyleSheet(
     ResourceIntegrityDisposition disposition =
         cachedStyleSheet->integrityDisposition();
 
-    DCHECK(disposition != ResourceIntegrityDisposition::NotChecked ||
-           !cachedStyleSheet->sheetText().isNull());
-
     if (disposition == ResourceIntegrityDisposition::NotChecked &&
         !cachedStyleSheet->loadFailedOrCanceled()) {
-      DCHECK(cachedStyleSheet->resourceBuffer());
-      if (SubresourceIntegrity::CheckSubresourceIntegrity(
-              *m_owner, cachedStyleSheet->resourceBuffer()->data(),
-              cachedStyleSheet->resourceBuffer()->size(), KURL(baseURL, href),
-              *cachedStyleSheet))
-        disposition = ResourceIntegrityDisposition::Passed;
-      else
-        disposition = ResourceIntegrityDisposition::Failed;
+      bool checkResult;
+      if (cachedStyleSheet->resourceBuffer()) {

[jww, 2016/10/14 17:42:11]

nit: This could be simplified by having a const char* data and size_t size
variables that are set based on if there is a resourceBuffer or not, and then
having one call to SubresourceIntegrity::CheckSubresourceIntegrity().

Definitely a style preference, though, so whatever you prefer.

[kouhei (in TOK), 2016/10/17 01:23:38]

Done.

+        checkResult = SubresourceIntegrity::CheckSubresourceIntegrity(
+            *m_owner, cachedStyleSheet->resourceBuffer()->data(),
+            cachedStyleSheet->resourceBuffer()->size(), KURL(baseURL, href),
+            *cachedStyleSheet);
+      } else {
+        // If resourceBuffer is nullptr, the resource content-size was 0.
+        checkResult = SubresourceIntegrity::CheckSubresourceIntegrity(
+            *m_owner, nullptr, 0, KURL(baseURL, href), *cachedStyleSheet);
+      }
+      disposition = checkResult ? ResourceIntegrityDisposition::Passed
+                                : ResourceIntegrityDisposition::Failed;
 
       // TODO(kouhei): Remove this const_cast crbug.com/653502
       const_cast<CSSStyleSheetResource*>(cachedStyleSheet)