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

src/debug/debug-coverage.h

 // Copyright 2017 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.
 
 #ifndef V8_DEBUG_DEBUG_COVERAGE_H_
 #define V8_DEBUG_DEBUG_COVERAGE_H_
 
 #include <vector>
 
 #include "src/debug/debug-interface.h"
@@ skipping 21 matching lines @@
   // Functions are sorted by start position, from outer to inner function.
   std::vector<CoverageFunction> functions;
 };
 
 class Coverage : public std::vector<CoverageScript> {
  public:
   // Allocate a new Coverage object and populate with result.
   // The ownership is transferred to the caller.
   static Coverage* Collect(Isolate* isolate, bool reset_count);
 
-  // Enable precise code coverage. This disables optimization and makes sure
-  // invocation count is not affected by GC.
-  static void TogglePrecise(Isolate* isolate, bool enable);
+  // Select code coverage mode.
+  static void SelectMode(Isolate* isolate, debug::Coverage::Mode mode);
 
  private:
   Coverage() {}
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_DEBUG_DEBUG_COVERAGE_H_