Expand WTF::StringView's API to be more like StringPiece.

third_party/WebKit/Source/wtf/text/WTFString.h

 /*
  * (C) 1999 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012, 2013 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 325 matching lines @@
 
     void ensure16Bit();
 
     void truncate(unsigned len);
     void remove(unsigned pos, int len = 1);
 
     String substring(unsigned pos, unsigned len = UINT_MAX) const;
     String left(unsigned len) const { return substring(0, len); }
     String right(unsigned len) const { return substring(length() - len, len); }
 
-    StringView createView() const { return StringView(impl()); }
-    StringView createView(unsigned offset, unsigned length) const { return StringView(impl(), offset, length); }
-
     // Returns a lowercase/uppercase version of the string
     String lower() const;
     String upper() const;
 
     String lower(const AtomicString& localeIdentifier) const;
     String upper(const AtomicString& localeIdentifier) const;
 
     String stripWhiteSpace() const;
     String stripWhiteSpace(IsWhiteSpaceFunctionPtr) const;
     String simplifyWhiteSpace(StripBehavior = StripExtraWhiteSpace) const;
@@ skipping 301 matching lines @@
     if (is8Bit()) {
         size_t oldSize = result.size();
         result.resize(oldSize + numberOfCharactersToCopy);
         memmove(result.data() + numberOfCharactersToCopy, result.data(), oldSize * sizeof(UChar));
         StringImpl::copyChars(result.data(), m_impl->characters8() + pos, numberOfCharactersToCopy);
     } else {
         result.prepend(m_impl->characters16() + pos, numberOfCharactersToCopy);
     }
 }
 
+inline StringView::StringView(const String& string)
+    : StringView(string, 0, string.length()) {}
+inline StringView::StringView(const String& string, unsigned offset, unsigned length)
+    : StringView(string.impl(), offset, length) {}
+inline StringView::StringView(const String& string, unsigned offset)
+    : StringView(string.impl(), offset) {}

[Yuta Kitamura, 2016/05/27 04:47:41]

Having inline definitions of StringView here looks strange.
If some files just include StringView.h but not WTFString.h,
uses of these constructors there will not get inlined
and you might end up weird link errors.

How about reversing the include dependency, i.e. remove
#include "wtf/StringView.h" from here and add #include
"WTFString.h" in StringView.h, and move the inline
definitions there? I think that's more natural and
intuitive.

This also applies other inlined constructors.

+
 // StringHash is the default hash for String
 template<typename T> struct DefaultHash;
 template<> struct DefaultHash<String> {
     typedef StringHash Hash;
 };
 
 // Shared global empty string.
 WTF_EXPORT const String& emptyString();
 WTF_EXPORT const String& emptyString16Bit();
 WTF_EXPORT extern const String& xmlnsWithColon;
@@ skipping 27 matching lines @@
 using WTF::charactersToFloat;
 using WTF::equal;
 using WTF::equalIgnoringCase;
 using WTF::find;
 using WTF::isAllSpecialCharacters;
 using WTF::isSpaceOrNewline;
 using WTF::reverseFind;
 
 #include "wtf/text/AtomicString.h"
 #endif // WTFString_h