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

third_party/WebKit/public/platform/WebString.h

 /*
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 102 matching lines @@
     {
         assign(fromUTF8(data, N - 1));
         return *this;
     }
 
 #if INSIDE_BLINK
     BLINK_COMMON_EXPORT WebString(const WTF::String&);
     BLINK_COMMON_EXPORT WebString& operator=(const WTF::String&);
     BLINK_COMMON_EXPORT operator WTF::String() const;
 
-    BLINK_COMMON_EXPORT operator WTF::StringView() const;
-
     BLINK_COMMON_EXPORT WebString(const WTF::AtomicString&);
     BLINK_COMMON_EXPORT WebString& operator=(const WTF::AtomicString&);
     BLINK_COMMON_EXPORT operator WTF::AtomicString() const;
 #else
     WebString(const base::string16& s)
     {
         assign(s.data(), s.length());
     }
 
     WebString& operator=(const base::string16& s)
@@ skipping 66 matching lines @@
 }
 
 inline bool operator!=(const WebString& a, const WebString& b)
 {
     return !(a == b);
 }
 
 } // namespace blink
 
 #endif