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

runtime/vm/code_generator.cc

 // Copyright (c) 2013, 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 "vm/code_generator.h"
 
 #include "vm/assembler.h"
 #include "vm/ast.h"
 #include "vm/code_patcher.h"
 #include "vm/compiler.h"
@@ skipping 1650 matching lines @@
     FLAG_stacktrace_every = saved_stacktrace_every;
   }
 
   const Error& error = Error::Handle(thread->HandleInterrupts());
   if (!error.IsNull()) {
     Exceptions::PropagateError(error);
     UNREACHABLE();
   }
 
   if ((stack_overflow_flags & Thread::kOsrRequest) != 0) {
-    ASSERT(FLAG_use_osr);
+    ASSERT(isolate->use_osr());
     DartFrameIterator iterator;
     StackFrame* frame = iterator.NextFrame();
     ASSERT(frame != NULL);
     const Code& code = Code::ZoneHandle(frame->LookupDartCode());
     ASSERT(!code.IsNull());
     ASSERT(!code.is_optimized());
     const Function& function = Function::Handle(code.function());
     ASSERT(!function.IsNull());
 
     // If the code of the frame does not match the function's unoptimized code,
@@ skipping 579 matching lines @@
   const intptr_t elm_size = old_data.ElementSizeInBytes();
   const TypedData& new_data =
       TypedData::Handle(TypedData::New(cid, new_size, Heap::kOld));
   TypedData::Copy(new_data, 0, old_data, 0, old_size * elm_size);
   typed_data_cell.SetAt(0, new_data);
   arguments.SetReturn(new_data);
 }
 
 
 }  // namespace dart