Move String::truncate to StringImpl.

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 f40a7cb76c293cbe6559e39b8da34e323782311f..54e9e937dcf162fbc0ebe3cbb67a4fb6da6dad51 100644
--- a/third_party/WebKit/Source/wtf/text/StringImpl.h
+++ b/third_party/WebKit/Source/wtf/text/StringImpl.h
@@ -338,6 +338,8 @@ public:
     // FIXME: Do we need fill(char) or can we just do the right thing if UChar is ASCII?
     PassRefPtr<StringImpl> foldCase();
 
+    PassRefPtr<StringImpl> truncate(unsigned length);
+
     PassRefPtr<StringImpl> stripWhiteSpace();
     PassRefPtr<StringImpl> stripWhiteSpace(IsWhiteSpaceFunctionPtr);
     PassRefPtr<StringImpl> simplifyWhiteSpace(StripBehavior = StripExtraWhiteSpace);