Lazy Parse CSS

third_party/WebKit/Source/core/css/parser/CSSLazyPropertyParserImpl.cpp

Index: third_party/WebKit/Source/core/css/parser/CSSLazyPropertyParserImpl.cpp
diff --git a/third_party/WebKit/Source/core/css/parser/CSSLazyPropertyParserImpl.cpp b/third_party/WebKit/Source/core/css/parser/CSSLazyPropertyParserImpl.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..5994663692aeff63bebfb9d91fa93dd1777fa7f0
--- /dev/null
+++ b/third_party/WebKit/Source/core/css/parser/CSSLazyPropertyParserImpl.cpp
@@ -0,0 +1,52 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "core/css/parser/CSSLazyPropertyParserImpl.h"
+
+#include "core/css/parser/CSSParserImpl.h"
+
+namespace blink {
+
+CSSLazyParsingState::CSSLazyParsingState(
+    const CSSParserContext& context,
+    std::unique_ptr<Vector<String>> escapedStrings,
+    const String& sheetText)
+    : m_context(context),
+      m_escapedStrings(std::move(escapedStrings)),
+      m_sheetText(sheetText) {}
+
+CSSLazyPropertyParserImpl::CSSLazyPropertyParserImpl(CSSParserTokenRange block,

[esprehn, 2016/10/24 21:20:20]

Can we put the classes in their own files?

[Charlie Harrison, 2016/10/25 15:56:55]

Done.

+                                                     CSSLazyParsingState* state)
+    : CSSLazyPropertyParser(), m_lazyState(state) {
+  // Reserve capacity to minimize heap bloat.
+  size_t length = block.end() - block.begin();
+  m_tokens.reserveCapacity(length);
+  m_tokens.append(block.begin(), length);
+}
+
+StylePropertySet* CSSLazyPropertyParserImpl::parseProperties() {
+  return CSSParserImpl::parseDeclarationListForLazyStyle(
+      m_tokens, m_lazyState->context());
+}
+
+//  Disallow lazy parsing for blocks which have
+//  - before/after in their selector list. This ensures we don't cause a
+//  collectFeatures() when we trigger parsing for attr() functions which would
+//  trigger expensive invalidation propagation.
+//
+//  Note: another optimization might be to disallow lazy parsing for rules which
+//  will end up being empty. This is hard to know without parsing but we may be
+//  able to catch the {}, { } cases. This would be to hit
+//  StyleRule::shouldConsiderForMatchingRules more.
+bool CSSLazyParsingState::shouldLazilyParseProperties(
+    const CSSSelectorList& selectors) {
+  for (const auto* s = selectors.first(); s; s = CSSSelectorList::next(*s)) {
+    const CSSSelector::PseudoType type(s->getPseudoType());
+    if (type == CSSSelector::PseudoBefore || type == CSSSelector::PseudoAfter)
+      return false;
+  }
+  return true;
+}
+
+}  // namespace blink