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

third_party/WebKit/Source/core/css/parser/CSSParserString.h

Index: third_party/WebKit/Source/core/css/parser/CSSParserString.h
diff --git a/third_party/WebKit/Source/core/css/parser/CSSParserString.h b/third_party/WebKit/Source/core/css/parser/CSSParserString.h
index 7b868fd9aee88e46c143b17e88e2ddc28e78bff4..58c12ed30a32903f7a5b4aeb15f5447809514b86 100644
--- a/third_party/WebKit/Source/core/css/parser/CSSParserString.h
+++ b/third_party/WebKit/Source/core/css/parser/CSSParserString.h
@@ -23,6 +23,7 @@
 
 #include "wtf/Allocator.h"
 #include "wtf/text/AtomicString.h"
+#include "wtf/text/StringView.h"
 #include "wtf/text/WTFString.h"
 
 namespace blink {
@@ -89,9 +90,12 @@ struct CSSParserString {
         return is8Bit() ? WTF::equalIgnoringASCIICase(characters8(), match, length()) : WTF::equalIgnoringASCIICase(characters16(), match, length());
     }
 
+    // TODO(esprehn): Remove both of these implicit operators, they're very expensive.
     operator String() const { return is8Bit() ? String(m_data.characters8, m_length) : StringImpl::create8BitIfPossible(m_data.characters16, m_length); }
     operator AtomicString() const { return is8Bit() ? AtomicString(m_data.characters8, m_length) : AtomicString(m_data.characters16, m_length); }
 
+    operator StringView() const { return is8Bit() ? StringView(m_data.characters8, m_length) : StringView(m_data.characters16, m_length); }
+
     union {
         const LChar* characters8;
         const UChar* characters16;