Bug 1207084 - keep sheet level on tokenstream for use in ruledata when resolving variables, to fix hcm issues with CSS variables, r=heycam

--HG--
extra : commitid : LOEulYWs1jS
extra : rebase_source : b9741e3bc6a4a762a2f6295d8d81069aca66745f
extra : amend_source : 13dd115d63546f57127fe65163c2aaacf8c6b043

layout/style/nsCSSDataBlock.cpp

@@ -262,6 +262,15 @@ nsCSSCompressedDataBlock::MapRuleInfoInto(nsRuleData *aRuleData) const
             nsCSSValue* target = aRuleData->ValueFor(iProp);
             if (target->GetUnit() == eCSSUnit_Null) {
                 const nsCSSValue *val = ValueAtIndex(i);
+                // In order for variable resolution to have the right information
+                // about the stylesheet level of a value, that level needs to be
+                // stored on the token stream. We can't do that at creation time
+                // because the CSS parser (which creates the object) has no idea
+                // about the stylesheet level, so we do it here instead, where
+                // the rule walking will have just updated aRuleData.
+                if (val->GetUnit() == eCSSUnit_TokenStream) {
+                  val->GetTokenStreamValue()->mLevel = aRuleData->mLevel;
+                }
                 MapSinglePropertyInto(iProp, val, target, aRuleData);
             }
         }

layout/style/nsCSSValue.cpp

@@ -23,6 +23,7 @@
 #include "nsPresContext.h"
 #include "nsStyleUtil.h"
 #include "nsDeviceContext.h"
+#include "nsStyleSet.h"
 
 using namespace mozilla;
 
@@ -2537,6 +2538,7 @@ nsCSSValueGradient::SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) con
 nsCSSValueTokenStream::nsCSSValueTokenStream()
   : mPropertyID(eCSSProperty_UNKNOWN)
   , mShorthandPropertyID(eCSSProperty_UNKNOWN)
+  , mLevel(nsStyleSet::eSheetTypeCount)
 {
   MOZ_COUNT_CTOR(nsCSSValueTokenStream);
 }

layout/style/nsCSSValue.h

@@ -1541,6 +1541,7 @@ public:
   // mozilla::CSSStyleSheet* mSheet;
   uint32_t mLineNumber;
   uint32_t mLineOffset;
+  uint16_t mLevel; // an nsStyleSet::sheetType
 
 private:
   nsCSSValueTokenStream(const nsCSSValueTokenStream& aOther) = delete;

layout/style/nsRuleNode.cpp

@@ -2180,6 +2180,12 @@ nsRuleNode::ResolveVariableReferences(const nsStyleStructID aSID,
       &aContext->StyleVariables()->mVariables;
     nsCSSValueTokenStream* tokenStream = value->GetTokenStreamValue();
 
+    MOZ_ASSERT(tokenStream->mLevel != nsStyleSet::eSheetTypeCount,
+               "Token stream should have a defined level");
+
+    AutoRestore<uint16_t> saveLevel(aRuleData->mLevel);
+    aRuleData->mLevel = tokenStream->mLevel;
+
     // Note that ParsePropertyWithVariableReferences relies on the fact
     // that the nsCSSValue in aRuleData for the property we are re-parsing
     // is still the token stream value.  When