[debugger] implement inspector-facing API for code coverage.

test/cctest/test-debug.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 6606 matching lines @@
                                       reinterpret_cast<void*>(isolate));
     CHECK(!out_of_memory_callback_called);
     // The following allocation fails unless the out-of-memory callback
     // increases the heap limit.
     int length = 10 * i::MB / i::kPointerSize;
     i_isolate->factory()->NewFixedArray(length, i::TENURED);
     CHECK(out_of_memory_callback_called);
   }
   isolate->Dispose();
 }
+
+TEST(DebugCoverage) {
+  i::FLAG_always_opt = false;
+  LocalContext env;
+  v8::Isolate* isolate = env->GetIsolate();
+  v8::HandleScope scope(isolate);
+  v8::debug::Coverage::TogglePrecise(isolate, true);
+  v8::Local<v8::String> source = v8_str(
+      "function f() {\n"
+      "}\n"
+      "f();\n"
+      "f();");
+  CompileRun(source);
+  v8::debug::Coverage coverage = v8::debug::Coverage::Collect(isolate);
+  CHECK_EQ(1u, coverage.ScriptCount());
+  v8::Local<v8::debug::Script> script = coverage.GetScript(0);
+  CHECK(script->Source()
+            .ToLocalChecked()
+            ->Equals(env.local(), source)
+            .FromMaybe(false));
+
+  v8::debug::Coverage::Range range = coverage.GetRange(0);
+  CHECK_EQ(0, range.Start().GetLineNumber());
+  CHECK_EQ(0, range.Start().GetColumnNumber());
+  CHECK_EQ(3, range.End().GetLineNumber());
+  CHECK_EQ(4, range.End().GetColumnNumber());
+  CHECK_EQ(1, range.Count());
+  CHECK_EQ(1u, range.NestedCount());
+
+  range = range.GetNested(0);
+  CHECK_EQ(0, range.Start().GetLineNumber());
+  CHECK_EQ(0, range.Start().GetColumnNumber());
+  CHECK_EQ(1, range.End().GetLineNumber());
+  CHECK_EQ(1, range.End().GetColumnNumber());
+  CHECK_EQ(2, range.Count());
+  CHECK_EQ(0, range.NestedCount());
+}