Stash ComputedStyles on new HeapHashMap on Document.

third_party/WebKit/Source/core/dom/Document.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2011, 2012 Apple Inc. All
  * rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved.
  * (http://www.torchmobile.com/)
  * Copyright (C) 2008, 2009, 2011, 2012 Google Inc. All rights reserved.
@@ skipping 1228 matching lines @@
 
       return body;
     }
 
     return documentElement();
   }
 
   return body();
 }
 
+// We use HashMap::set over HashMap::add here as we want to
+// replace the ComputedStyle but not the Element if the Element is
+// already present.
+void Document::addNonAttachedStyle(Element* element,
+                                   RefPtr<ComputedStyle> computedStyle) {
+  m_nonAttachedStyle.set(element, computedStyle);
+}
+
+RefPtr<ComputedStyle> Document::getNonAttachedStyle(Element* element) {
+  return m_nonAttachedStyle.get(element);
+}
+
+void Document::clear() {

[esprehn, 2016/10/05 01:04:25]

Remove this function, you can't add something so generic as clear() to Document.

[nainar, 2016/10/05 02:00:01]

Done.

+  for (NonAttachedStyleMap::iterator iter = m_nonAttachedStyle.begin();
+       iter != m_nonAttachedStyle.end(); ++iter)
+    m_nonAttachedStyle.remove(iter);

[esprehn, 2016/10/05 01:04:25]

m_nonAttachedStyle.clear(), note that calling remove() like this on a hash map
is not allowed. You can't mutate the hash map while you're iterating. This is
also going to be very slow since you're causing the hashmap to repeatedly resize

[nainar, 2016/10/05 02:00:01]

Done.

+}
+
 /*
  * Performs three operations:
  *  1. Convert control characters to spaces
  *  2. Trim leading and trailing spaces
  *  3. Collapse internal whitespace.
  */
 template <typename CharacterType>
 static inline String canonicalizedTitle(Document* document,
                                         const String& title) {
   unsigned length = title.length();
@@ skipping 610 matching lines @@
 void Document::updateStyle() {
   DCHECK(!view()->shouldThrottleRendering());
   TRACE_EVENT_BEGIN0("blink,blink_style", "Document::updateStyle");
   SCOPED_BLINK_UMA_HISTOGRAM_TIMER("Style.UpdateTime");
 
   unsigned initialElementCount = styleEngine().styleForElementCount();
 
   HTMLFrameOwnerElement::UpdateSuspendScope suspendWidgetHierarchyUpdates;
   m_lifecycle.advanceTo(DocumentLifecycle::InStyleRecalc);
 
+  // Reserving capacity to avoid rehashes.
+  m_nonAttachedStyle.reserveCapacityForSize(initialElementCount);

[esprehn, 2016/10/05 01:04:25]

initialElementCount doesn't mean what you think it does, it's the number of
times we called styleForElement in recalcStyle (for all time). That number is
ever increasing, which means you're creating a bigger and bigger hash map here
every time.

I'd leave this out

[nainar, 2016/10/05 02:00:01]

Done.

+
   StyleRecalcChange change = NoChange;
   if (getStyleChangeType() >= SubtreeStyleChange)
     change = Force;
 
   NthIndexCache nthIndexCache(*this);
 
   // FIXME: Cannot access the ensureStyleResolver() before calling
   // styleForDocument below because apparently the StyleResolver's constructor
   // has side effects. We should fix it.  See printing/setPrinting.html,
   // printing/width-overflow.html though they only fail on mac when accessing
@@ skipping 21 matching lines @@
     inheritHtmlAndBodyElementStyles(change);
     dirtyElementsForLayerUpdate();
     if (documentElement->shouldCallRecalcStyle(change))
       documentElement->recalcStyle(change);
     while (dirtyElementsForLayerUpdate())
       documentElement->recalcStyle(NoChange);
   }
 
   view()->recalcOverflowAfterStyleChange();
 
+  // Only retain the HashMap for the duration of StyleRecalc and
+  // LayoutTreeConstruction.
+  m_nonAttachedStyle.clear();
   clearChildNeedsStyleRecalc();
 
   resolver.clearStyleSharingList();
 
   m_wasPrinting = m_printing;
 
   DCHECK(!needsStyleRecalc());
   DCHECK(!childNeedsStyleRecalc());
   DCHECK(inStyleRecalc());
   DCHECK_EQ(styleResolver(), &resolver);
+  DCHECK(m_nonAttachedStyle.isEmpty());
   m_lifecycle.advanceTo(DocumentLifecycle::StyleClean);
   if (shouldRecordStats) {
     TRACE_EVENT_END2("blink,blink_style", "Document::updateStyle",
                      "resolverAccessCount",
                      styleEngine().styleForElementCount() - initialElementCount,
                      "counters", styleEngine().stats()->toTracedValue());
   } else {
     TRACE_EVENT_END1(
         "blink,blink_style", "Document::updateStyle", "resolverAccessCount",
         styleEngine().styleForElementCount() - initialElementCount);
@@ skipping 4379 matching lines @@
   visitor->trace(m_svgExtensions);
   visitor->trace(m_timeline);
   visitor->trace(m_compositorPendingAnimations);
   visitor->trace(m_contextDocument);
   visitor->trace(m_canvasFontCache);
   visitor->trace(m_intersectionObserverController);
   visitor->trace(m_intersectionObserverData);
   visitor->trace(m_snapCoordinator);
   visitor->trace(m_resizeObserverController);
   visitor->trace(m_propertyRegistry);
+  visitor->trace(m_nonAttachedStyle);
   Supplementable<Document>::trace(visitor);
   TreeScope::trace(visitor);
   ContainerNode::trace(visitor);
   ExecutionContext::trace(visitor);
   SecurityContext::trace(visitor);
 }
 
 void Document::onVisibilityMaybeChanged(bool visible) {
   DCHECK(frame());
   if (visible && !m_visibilityWasLogged && frame()->isCrossOriginSubframe()) {
@@ skipping 30 matching lines @@
 }
 
 void showLiveDocumentInstances() {
   WeakDocumentSet& set = liveDocumentSet();
   fprintf(stderr, "There are %u documents currently alive:\n", set.size());
   for (Document* document : set)
     fprintf(stderr, "- Document %p URL: %s\n", document,
             document->url().getString().utf8().data());
 }
 #endif