Use weak members to cache StyleSheetContents.

third_party/WebKit/Source/core/css/StyleSheetContents.cpp

Index: third_party/WebKit/Source/core/css/StyleSheetContents.cpp
diff --git a/third_party/WebKit/Source/core/css/StyleSheetContents.cpp b/third_party/WebKit/Source/core/css/StyleSheetContents.cpp
index a3a7b8ff31a319af23ec78c0e0546a2d33e254b9..9ad890082c3cc4b20fc52366b5317ba5fd16ad06 100644
--- a/third_party/WebKit/Source/core/css/StyleSheetContents.cpp
+++ b/third_party/WebKit/Source/core/css/StyleSheetContents.cpp
@@ -65,6 +65,7 @@ StyleSheetContents::StyleSheetContents(StyleRuleImport* ownerRule, const String&
     , m_hasFontFaceRule(false)
     , m_hasMediaQueries(false)
     , m_hasSingleOwnerDocument(true)
+    , m_isUsedFromTextCache(false)
     , m_parserContext(context)
 {
 }
@@ -83,6 +84,7 @@ StyleSheetContents::StyleSheetContents(const StyleSheetContents& o)
     , m_hasFontFaceRule(o.m_hasFontFaceRule)
     , m_hasMediaQueries(o.m_hasMediaQueries)
     , m_hasSingleOwnerDocument(true)
+    , m_isUsedFromTextCache(false)
     , m_parserContext(o.m_parserContext)
 {
     // FIXME: Copy import rules.
@@ -98,10 +100,6 @@ StyleSheetContents::~StyleSheetContents()
 
 void StyleSheetContents::setHasSyntacticallyValidCSSHeader(bool isValidCss)
 {
-    if (!isValidCss) {
-        if (Document* document = clientSingleOwnerDocument())
-            removeSheetFromCache(document);

[haraken, 2016/08/03 01:01:18]

For example, don't you need to explicitly remove the sheet from the cache here?

[rune, 2016/08/03 09:20:05]

I think that removeSheetFromCache here never removed anything because ending up
here for a stylesheet which is already in the cache should be guarded by a
RuleMutationScope which calls willMutateRules(). willMutateRules() used to
remove the StyleSheetContents from the cache. I have removed the explicit remove
from there as well. What happens in willMutateRules() is that the contents will
be setMutable() if there's only one sheet referring to it, and otherwise cloned
before modified. If the in-cache contents is set mutable, it will not be
cacheable and the cache-entry will be replaced if we try to create a sheet with
the same text again.

-    }
     m_hasSyntacticallyValidCSSHeader = isValidCss;
 }
 
@@ -546,8 +544,6 @@ void StyleSheetContents::unregisterClient(CSSStyleSheet* sheet)
     if (!sheet->ownerDocument() || !m_loadingClients.isEmpty() || !m_completedClients.isEmpty())
         return;
 
-    if (m_hasSingleOwnerDocument)
-        removeSheetFromCache(sheet->ownerDocument());
     m_hasSingleOwnerDocument = true;
 }
 
@@ -570,12 +566,6 @@ void StyleSheetContents::clientLoadStarted(CSSStyleSheet* sheet)
     m_loadingClients.add(sheet);
 }
 
-void StyleSheetContents::removeSheetFromCache(Document* document)
-{
-    ASSERT(document);
-    document->styleEngine().removeSheet(this);
-}
-
 void StyleSheetContents::setReferencedFromResource(CSSStyleSheetResource* resource)
 {
     DCHECK(resource);