Improve compilation speed on a pathological case > 2x (7 sec -> 2.7 sec) by improving local lookups.

runtime/vm/object_test.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/assert.h"
 #include "vm/assembler.h"
 #include "vm/bigint_operations.h"
 #include "vm/class_finalizer.h"
 #include "vm/isolate.h"
 #include "vm/object.h"
@@ skipping 2470 matching lines @@
 TEST_CASE(ContextScope) {
   const intptr_t parent_scope_function_level = 0;
   LocalScope* parent_scope =
       new LocalScope(NULL, parent_scope_function_level, 0);
 
   const intptr_t local_scope_function_level = 1;
   LocalScope* local_scope =
       new LocalScope(parent_scope, local_scope_function_level, 0);
 
   const Type& dynamic_type = Type::ZoneHandle(Type::DynamicType());
-  const String& a = String::ZoneHandle(String::New("a"));
+  const String& a = String::ZoneHandle(Symbols::New("a"));
   LocalVariable* var_a =
       new LocalVariable(Scanner::kDummyTokenIndex, a, dynamic_type);
   parent_scope->AddVariable(var_a);
 
-  const String& b = String::ZoneHandle(String::New("b"));
+  const String& b = String::ZoneHandle(Symbols::New("b"));
   LocalVariable* var_b =
       new LocalVariable(Scanner::kDummyTokenIndex, b, dynamic_type);
   local_scope->AddVariable(var_b);
 
-  const String& c = String::ZoneHandle(String::New("c"));
+  const String& c = String::ZoneHandle(Symbols::New("c"));
   LocalVariable* var_c =
       new LocalVariable(Scanner::kDummyTokenIndex, c, dynamic_type);
   parent_scope->AddVariable(var_c);
 
   bool test_only = false;  // Please, insert alias.
   var_a = local_scope->LookupVariable(a, test_only);
   EXPECT(var_a->is_captured());
   EXPECT_EQ(parent_scope_function_level, var_a->owner()->function_level());
   EXPECT(local_scope->LocalLookupVariable(a) == var_a);  // Alias.
 
@@ skipping 1036 matching lines @@
   EXPECT_NE(test1.SourceFingerprint(), test3.SourceFingerprint());
   EXPECT_NE(test3.SourceFingerprint(), test4.SourceFingerprint());
   EXPECT_NE(test4.SourceFingerprint(), test5.SourceFingerprint());
   EXPECT_NE(test5.SourceFingerprint(), test6.SourceFingerprint());
   EXPECT_EQ(test6.SourceFingerprint(), test7.SourceFingerprint());
 }
 
 #endif  // defined(TARGET_ARCH_IA32) || defined(TARGET_ARCH_X64).
 
 }  // namespace dart