Tidy DEFINE_(THREAD_SAFE_)STATIC_LOCAL() implementations.

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

Index: third_party/WebKit/Source/core/html/HTMLTableElement.cpp
diff --git a/third_party/WebKit/Source/core/html/HTMLTableElement.cpp b/third_party/WebKit/Source/core/html/HTMLTableElement.cpp
index 6d507ba3f0712a285d36db17bfa20c961dd39415..33162549edbe422699d15c50139458fc469bc8cc 100644
--- a/third_party/WebKit/Source/core/html/HTMLTableElement.cpp
+++ b/third_party/WebKit/Source/core/html/HTMLTableElement.cpp
@@ -453,8 +453,20 @@ HTMLTableElement::additionalPresentationAttributeStyle() {
     // Setting the border to 'hidden' allows it to win over any border
     // set on the table's cells during border-conflict resolution.
     if (m_rulesAttr != UnsetRules) {
+      // Note: this (Mutable)StylePropertySet singleton has an embedded
+      // CSSStyleDeclaration reference (m_cssomWrapper), which is a
+      // ScriptWrappable (=> it can have a v8 wrapper object). Exposing
+      // and sharing those via static locals is unsafe, as the singleton
+      // really is accessible across window contexts within a renderer
+      // process.
+      //
+      // However, that CSSStyleDeclaration is never instantiated for these
+      // presentation attribute style properties, hence this singleton (and
+      // the ones below) are considered safe. Indicate that by disabling
+      // the no-ScriptWrappables-in-singletons verification check.

[haraken, 2017/02/11 10:25:20]

Your analysis looks correct, but it looks better to avoid using
DEFINE_STATIC_LOCAL... by e.g., associating the StylePropertySet with Document
(or StyleEngine) etc.

[sof, 2017/02/11 12:09:11]

That could probably be done without it being too ad-hoc.

       DEFINE_STATIC_LOCAL(StylePropertySet, solidBorderStyle,
-                          (createBorderStyle(CSSValueHidden)));
+                          (createBorderStyle(CSSValueHidden)),
+                          CheckScriptWrappable::No);
       return &solidBorderStyle;
     }
     return nullptr;
@@ -462,11 +474,13 @@ HTMLTableElement::additionalPresentationAttributeStyle() {
 
   if (m_borderColorAttr) {
     DEFINE_STATIC_LOCAL(StylePropertySet, solidBorderStyle,
-                        (createBorderStyle(CSSValueSolid)));
+                        (createBorderStyle(CSSValueSolid)),
+                        CheckScriptWrappable::No);
     return &solidBorderStyle;
   }
   DEFINE_STATIC_LOCAL(StylePropertySet, outsetBorderStyle,
-                      (createBorderStyle(CSSValueOutset)));
+                      (createBorderStyle(CSSValueOutset)),
+                      CheckScriptWrappable::No);
   return &outsetBorderStyle;
 }
 
@@ -570,11 +584,13 @@ const StylePropertySet* HTMLTableElement::additionalGroupStyle(bool rows) {
 
   if (rows) {
     DEFINE_STATIC_LOCAL(StylePropertySet, rowBorderStyle,
-                        (createGroupBorderStyle(true)));
+                        (createGroupBorderStyle(true)),
+                        CheckScriptWrappable::No);
     return &rowBorderStyle;
   }
   DEFINE_STATIC_LOCAL(StylePropertySet, columnBorderStyle,
-                      (createGroupBorderStyle(false)));
+                      (createGroupBorderStyle(false)),
+                      CheckScriptWrappable::No);
   return &columnBorderStyle;
 }