VM: Make use_osr an Isolate flag, similar to how we made use_field_guards.

runtime/vm/debugger_api_impl_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 "include/dart_mirrors_api.h"
 #include "include/dart_tools_api.h"
 #include "platform/assert.h"
 #include "vm/dart_api_impl.h"
 #include "vm/lockers.h"
 #include "vm/unit_test.h"
@@ skipping 447 matching lines @@
       "  return middleMan(5, limit, stop);\n"
       "}\n";
 
   LoadScript(kScriptChars);
 
   // Save/restore some compiler flags.
   Dart_Handle dart_args[2];
   int saved_threshold = FLAG_optimization_counter_threshold;
   const int kLowThreshold = 100;
   const int kHighThreshold = 10000;
-  bool saved_osr = FLAG_use_osr;
-  FLAG_use_osr = false;
+  Isolate* isolate = Isolate::Current();
+  const bool saved_use_osr = isolate->use_osr();
+  isolate->set_use_osr(false);
 
   if (optimize) {
     // Warm up the code to make sure it gets optimized.  We ignore any
     // breakpoints that get hit during warm-up.
     FLAG_optimization_counter_threshold = kLowThreshold;
     dart_args[0] = Dart_False();
     dart_args[1] = Dart_NewInteger(kLowThreshold);
     EXPECT_VALID(Dart_Invoke(script_lib, NewString("test"), 2, dart_args));
   } else {
     // Try to ensure that none of the test code gets optimized.
@@ skipping 24 matching lines @@
         "[0] breakpointNow { }\n"
         "[1] helper { a = 5 b = 99 stop = true }\n"
         "[2] anotherMiddleMan { one = 5 two = 99 stop = true }\n"
         "[3] middleMan { x = 5 limit = 100 stop = true value = 24255"
         " i = 99 }\n"
         "[4] test { stop = true limit = 100 }\n",
         stack_buffer);
   }
 
   FLAG_optimization_counter_threshold = saved_threshold;
-  FLAG_use_osr = saved_osr;
+  isolate->set_use_osr(saved_use_osr);
 }
 
 
 TEST_CASE(Debug_InspectStack_NotOptimized) {
   InspectStackTest(false);
 }
 
 
 TEST_CASE(Debug_InspectStack_Optimized) {
   // Ensure code gets optimized.
@@ skipping 1831 matching lines @@
       " null, 5, 17, 5, 18, 9, 19, 12,"
       " null, 6, 21, 1,"
       " null, 8, 24, 1, 25, 5, 26, 6, 27, 8,"
       " null, 9, 29, 1]",
       tokens_cstr);
 }
 
 #endif
 
 }  // namespace dart