Lazy Parse CSS

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

Index: third_party/WebKit/Source/core/css/StyleRule.cpp
diff --git a/third_party/WebKit/Source/core/css/StyleRule.cpp b/third_party/WebKit/Source/core/css/StyleRule.cpp
index ffc73fe80bc83c10d6dd96c826c9646bb7d9eb7e..797dc0ce6ab6dd86292c21816a44d2923566bfdb 100644
--- a/third_party/WebKit/Source/core/css/StyleRule.cpp
+++ b/third_party/WebKit/Source/core/css/StyleRule.cpp
@@ -212,15 +212,31 @@ unsigned StyleRule::averageSizeInBytes()
 
 StyleRule::StyleRule(CSSSelectorList selectorList, StylePropertySet* properties)
     : StyleRuleBase(Style)
+    , m_selectorList(std::move(selectorList))
     , m_properties(properties)
 {
-    m_selectorList = std::move(selectorList);
+}
+
+StyleRule::StyleRule(CSSSelectorList selectorList, std::unique_ptr<CSSParser::DeferredPropertiesClosure> deferredProperties)
+    : StyleRuleBase(Style)
+    , m_selectorList(std::move(selectorList))
+    , m_deferred(std::move(deferredProperties))
+{
+}
+
+const StylePropertySet& StyleRule::properties() const
+{
+    if (!m_properties) {
+        m_properties = (*m_deferred)();

[Timothy Loh, 2016/09/26 05:18:00]

Should we clear the escaped string store since it won't be used again?

[Charlie Harrison, 2016/09/26 22:14:45]

Unfortunately the escaped string pool has *all* the escaped strings from
tokenizing, so as the CL is currently designed we won't be able to clear it
until all properties are lazily parsed.

Two possible solutions:
 - don't lazily parse properties which use escaped strings
 - do a string copy and store the escaped string with the closure

Both solutions would require changing the tokenizer in ways I haven't fully
thought through (would we need to add an extra bool "hasEscapedString" to all
tokens?)

[Timothy Loh, 2016/09/27 05:15:45]

Oh right, it's fine as is then :)

+        m_deferred.reset();
+    }
+    return *m_properties;
 }
 
 StyleRule::StyleRule(const StyleRule& o)
     : StyleRuleBase(o)
-    , m_properties(o.m_properties->mutableCopy())
     , m_selectorList(o.m_selectorList.copy())
+    , m_properties(o.properties().mutableCopy())
 {
 }
 
@@ -230,11 +246,25 @@ StyleRule::~StyleRule()
 
 MutableStylePropertySet& StyleRule::mutableProperties()
 {
-    if (!m_properties->isMutable())
-        m_properties = m_properties->mutableCopy();
+    // Ensure m_properties is initialized.
+    const StylePropertySet& props = properties();
+    if (!props.isMutable())
+        m_properties = props.mutableCopy();
     return *toMutableStylePropertySet(m_properties.get());
 }
 
+bool StyleRule::propertiesHaveFailedOrCanceledSubresources() const
+{
+    return m_properties && m_properties->hasFailedOrCanceledSubresources();
+}
+
+bool StyleRule::hasEmptyProperties() const
+{
+    // We only lazily parse if the property block has a nonzero amount of
+    // tokens. Thus, consider all lazily initialized properties to be non-empty.
+    return m_properties && m_properties->isEmpty();
+}
+
 DEFINE_TRACE_AFTER_DISPATCH(StyleRule)
 {
     visitor->trace(m_properties);