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

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

Index: third_party/WebKit/Source/wtf/text/StringImpl.h
diff --git a/third_party/WebKit/Source/wtf/text/StringImpl.h b/third_party/WebKit/Source/wtf/text/StringImpl.h
index eaf077a7371ca90940ca996c9327900bc18c478d..a0bcc9a227c4b7a2b083b409c374a2a12983d392 100644
--- a/third_party/WebKit/Source/wtf/text/StringImpl.h
+++ b/third_party/WebKit/Source/wtf/text/StringImpl.h
@@ -29,6 +29,7 @@
 #include "wtf/StringHasher.h"
 #include "wtf/Vector.h"
 #include "wtf/WTFExport.h"
+#include "wtf/text/StringView.h"
 #include "wtf/text/Unicode.h"
 #include <limits.h>
 
@@ -743,6 +744,32 @@ inline PassRefPtr<StringImpl> StringImpl::isolatedCopy() const
     return create(characters16(), m_length);
 }
 
+inline void StringView::set(StringImpl& impl, unsigned offset, unsigned length)
+{
+    SECURITY_DCHECK(offset + length <= impl.length());
+    m_length = length;
+    m_is8Bit = impl.is8Bit();
+    if (m_is8Bit)
+        m_data.characters8 = impl.characters8() + offset;
+    else
+        m_data.characters16 = impl.characters16() + offset;
+}
+
+inline StringView::StringView(StringImpl* impl)
+{
+    impl ? set(*impl, 0, impl->length()) : clear();
+}
+
+inline StringView::StringView(StringImpl* impl, unsigned offset)
+{
+    impl ? set(*impl, offset, impl->length()) : clear();
+}
+
+inline StringView::StringView(StringImpl* impl, unsigned offset, unsigned length)
+{
+    impl ? set(*impl, offset, length) : clear();
+}
+
 // TODO(rob.buis) possibly find a better place for this method.
 // Turns a UChar32 to uppercase based on localeIdentifier.
 WTF_EXPORT UChar32 toUpper(UChar32, const AtomicString& localeIdentifier);