Reduce the perf overhead of our dangling markup experiments.

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 4927 matching lines @@
       layoutViewItem().mutableStyleRef().setRtlOrdering(
           m_visuallyOrdered ? EOrder::kVisual : EOrder::kLogical);
     }
     setNeedsStyleRecalc(SubtreeStyleChange,
                         StyleChangeReasonForTracing::create(
                             StyleChangeReason::VisuallyOrdered));
   }
 }
 
 KURL Document::completeURL(const String& url) const {
-  String trimmed = url.stripWhiteSpace();
   KURL completed = completeURLWithOverride(url, m_baseURL);
 
-  bool newline = trimmed.contains('\n') || trimmed.contains('\r');
-  bool lessThan = trimmed.contains('<');
-  if ((newline || lessThan) && completed.protocolIsInHTTPFamily()) {
-    if (newline) {
+  if (completed.whitespaceRemoved()) {

[Charlie Harrison, 2017/01/19 13:06:49]

Optional: I think an early return here would be nicer stylistically, as it is
the common case to have no whitespace.

+    if (completed.protocolIsInHTTPFamily()) {
       UseCounter::count(*this,
                         UseCounter::DocumentCompleteURLHTTPContainingNewline);
+      bool lessThan = url.contains('<');
+      if (lessThan) {
+        UseCounter::count(
+            *this,
+            UseCounter::DocumentCompleteURLHTTPContainingNewlineAndLessThan);
+
+        if (RuntimeEnabledFeatures::restrictCompleteURLCharacterSetEnabled())
+          return KURL();
+      }
+    } else {
+      UseCounter::count(
+          *this, UseCounter::DocumentCompleteURLNonHTTPContainingNewline);
     }
-    if (lessThan) {
-      UseCounter::count(*this,
-                        UseCounter::DocumentCompleteURLHTTPContainingLessThan);
-    }
-    if (newline && lessThan) {
-      UseCounter::count(
-          *this,
-          UseCounter::DocumentCompleteURLHTTPContainingNewlineAndLessThan);
-
-      if (RuntimeEnabledFeatures::restrictCompleteURLCharacterSetEnabled())
-        return KURL();
-    }
-  } else if (newline || lessThan) {
-    UseCounter::count(
-        *this,
-        UseCounter::DocumentCompleteURLNonHTTPContainingNewlineOrLessThan);
   }
-  return completeURLWithOverride(url, m_baseURL);
+  return completed;
 }
 
 KURL Document::completeURLWithOverride(const String& url,
                                        const KURL& baseURLOverride) const {
   DCHECK(baseURLOverride.isEmpty() || baseURLOverride.isValid());
 
   // Always return a null URL when passed a null string.
   // FIXME: Should we change the KURL constructor to have this behavior?
   // See also [CSS]StyleSheet::completeURL(const String&)
   if (url.isNull())
@@ skipping 1552 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