[debug] refactor code coverage to use enum for mode.

src/runtime/runtime-debug.cc

 // Copyright 2014 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/runtime/runtime-utils.h"
 
 #include "src/arguments.h"
 #include "src/compiler.h"
 #include "src/debug/debug-coverage.h"
 #include "src/debug/debug-evaluate.h"
@@ skipping 1927 matching lines @@
     Handle<JSObject> wrapper = Script::GetWrapper(script_data.script);
     JSObject::AddProperty(script_obj, script_string, wrapper, NONE);
     scripts_array->set(i, *script_obj);
   }
   return *factory->NewJSArrayWithElements(scripts_array, FAST_ELEMENTS);
 }
 
 RUNTIME_FUNCTION(Runtime_DebugTogglePreciseCoverage) {
   SealHandleScope shs(isolate);
   CONVERT_BOOLEAN_ARG_CHECKED(enable, 0);
-  Coverage::TogglePrecise(isolate, enable);
+  Coverage::SelectMode(isolate, enable ? debug::Coverage::kPreciseCount
+                                       : debug::Coverage::kBestEffort);
   return isolate->heap()->undefined_value();
 }
 
 }  // namespace internal
 }  // namespace v8