[builtins] Migrate String.prototype.trim/trimLeft/trimRight to C++.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 24436f735ce89141de45a18086f18b1d4c646d67..d640ced23688e6659f56cf92aca726c3f46b923e 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -8860,6 +8860,10 @@ class String: public Name {
   // Conversion.
   inline bool AsArrayIndex(uint32_t* index);
 
+  // Trimming.
+  enum TrimMode { kTrim, kTrimLeft, kTrimRight };
+  static Handle<String> Trim(Handle<String> string, TrimMode mode);
+
   DECLARE_CAST(String)
 
   void PrintOn(FILE* out);