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

src/objects.cc

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/objects.h"
 
 #include <cmath>
 #include <iomanip>
 #include <sstream>
 
@@ skipping 9964 matching lines @@
   if (IsEmpty()) return other->IsEmpty();
   if (other->IsEmpty()) return false;
   if (length() != other->length()) return false;
   for (int i = 0; i < length(); ++i) {
     if (get(i) != other->get(i)) return false;
   }
   return true;
 }
 #endif
 
+// static
+Handle<String> String::Trim(Handle<String> string, TrimMode mode) {
+  Isolate* const isolate = string->GetIsolate();
+  string = String::Flatten(string);
+  int const length = string->length();
+
+  // Perform left trimming if requested.
+  int left = 0;
+  UnicodeCache* unicode_cache = isolate->unicode_cache();
+  if (mode == kTrim || mode == kTrimLeft) {
+    while (left < length &&
+           unicode_cache->IsWhiteSpaceOrLineTerminator(string->Get(left))) {
+      left++;
+    }
+  }
+
+  // Perform right trimming if requested.
+  int right = length;
+  if (mode == kTrim || mode == kTrimRight) {
+    while (
+        right > left &&
+        unicode_cache->IsWhiteSpaceOrLineTerminator(string->Get(right - 1))) {
+      right--;
+    }
+  }
+
+  return isolate->factory()->NewSubString(string, left, right);
+}
 
 bool String::LooksValid() {
   if (!GetIsolate()->heap()->Contains(this)) return false;
   return true;
 }
 
 
 // static
 MaybeHandle<String> Name::ToFunctionName(Handle<Name> name) {
   if (name->IsString()) return Handle<String>::cast(name);
@@ skipping 8530 matching lines @@
   if (cell->value() != *new_value) {
     cell->set_value(*new_value);
     Isolate* isolate = cell->GetIsolate();
     cell->dependent_code()->DeoptimizeDependentCodeGroup(
         isolate, DependentCode::kPropertyCellChangedGroup);
   }
 }
 
 }  // namespace internal
 }  // namespace v8