Avoid copying strings when parsing CSS colors on the slow path.

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

 // Copyright 2014 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/CSSTokenizer.h"
 
 namespace blink {
 #include "core/CSSTokenizerCodepoints.cpp"
 }
 
@@ skipping 649 matching lines @@
     }
     return false;
 }
 
 // http://www.w3.org/TR/css3-syntax/#consume-a-name
 StringView CSSTokenizer::consumeName()
 {
     // Names without escapes get handled without allocations
     for (unsigned size = 0; ; ++size) {
         UChar cc = m_input.peekWithoutReplacement(size);
-        if (cc == '\0' || cc == '\\')
+        if (isNameCodePoint(cc))
+            continue;
+        // peekWithoutReplacement will return NUL when we hit the end of the
+        // input. In that case we want to still use the rangeAt() fast path
+        // below.
+        if (cc == '\0' && m_input.offset() + size < m_input.length())

[Timothy Loh, 2016/06/27 00:14:25]

good find!

             break;
-        if (!isNameCodePoint(cc)) {
-            unsigned startOffset = m_input.offset();
-            m_input.advance(size);
-            return m_input.rangeAt(startOffset, size);
-        }
+        if (cc == '\\')
+            break;
+        unsigned startOffset = m_input.offset();
+        m_input.advance(size);
+        return m_input.rangeAt(startOffset, size);
     }
 
     StringBuilder result;
     while (true) {
         UChar cc = consume();
         if (isNameCodePoint(cc)) {
             result.append(cc);
             continue;
         }
         if (twoCharsAreValidEscape(cc, m_input.nextInputChar())) {
@@ skipping 80 matching lines @@
     return areIdentifier;
 }
 
 StringView CSSTokenizer::registerString(const String& string)
 {
     m_scope.storeString(string);
     return string;
 }
 
 } // namespace blink