[wasm] Improve pimpl implementation in WasmInterpreter::Thread

src/wasm/wasm-interpreter.h

 // Copyright 2016 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_WASM_INTERPRETER_H_
 #define V8_WASM_INTERPRETER_H_
 
 #include "src/wasm/wasm-opcodes.h"
 #include "src/zone/zone-containers.h"
 
@@ skipping 95 matching lines @@
   //                       V                               |
   // STOPPED ---Run()-->  RUNNING  ------Pause()-----+-> PAUSED  <------+
   //                       | | |                    /      |            |
   //                       | | +---- Breakpoint ---+       +-- Step() --+
   //                       | |
   //                       | +------------ Trap --------------> TRAPPED
   //                       +------------- Finish -------------> FINISHED
   enum State { STOPPED, RUNNING, PAUSED, FINISHED, TRAPPED };
 
   // Representation of a thread in the interpreter.
-  class ThreadImpl;
   class V8_EXPORT_PRIVATE Thread {
-    ThreadImpl* impl_;
+    // Don't instante Threads; they will be allocated as ThreadImpl in the
+    // interpreter implementation.
+    Thread() = delete;
 
    public:
-    explicit Thread(ThreadImpl*);
-
     // Execution control.
     State state();
     void PushFrame(const WasmFunction* function, WasmVal* args);
     State Run();
     State Step();
     void Pause();
     void Reset();
 
     // Stack inspection and modification.
     pc_t GetBreakpointPc();
@@ skipping 71 matching lines @@
  private:
   Zone zone_;
   WasmInterpreterInternals* internals_;
 };
 
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_WASM_INTERPRETER_H_