[wasm] Implement stepping in wasm code

src/debug/debug.js

 // Copyright 2012 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.
 
 (function (global, utils) {
 "use strict";
 
 // ----------------------------------------------------------------------------
 // Imports
 
@@ skipping 1275 matching lines @@
   } catch (e) {
     // Failed in one of the catch blocks above - most generic error.
     return '{"seq":0,"type":"response","success":false,"message":"Internal error"}';
   }
 };
 
 
 DebugCommandProcessor.prototype.continueRequest_ = function(request, response) {
   // Check for arguments for continue.
   if (request.arguments) {
-    var action = Debug.StepAction.StepIn;
-
     // Pull out arguments.
     var stepaction = request.arguments.stepaction;
 
     // Get the stepaction argument.
     if (stepaction) {

[titzer, 2017/01/23 10:10:10]

This can probably be further simplified to just be a switch with a default case,
and no if.

[Clemens Hammacher, 2017/01/23 12:25:34]

Yang just removed this whole code anyway :)

+      var action;
       if (stepaction == 'in') {
         action = Debug.StepAction.StepIn;
       } else if (stepaction == 'next') {
         action = Debug.StepAction.StepNext;
       } else if (stepaction == 'out') {
         action = Debug.StepAction.StepOut;
       } else {
         throw %make_error(kDebugger,
                         'Invalid stepaction argument "' + stepaction + '".');
       }
+
+      // Set up the VM for stepping.
+      this.exec_state_.prepareStep(action);
     }
-
-    // Set up the VM for stepping.
-    this.exec_state_.prepareStep(action);
   }
 
   // VM should be running after executing this request.
   response.running = true;
 };
 
 
 DebugCommandProcessor.prototype.breakRequest_ = function(request, response) {
   // Ignore as break command does not do anything when broken.
 };
@@ skipping 1057 matching lines @@
 utils.InstallFunctions(utils, DONT_ENUM, [
   "MakeExecutionState", MakeExecutionState,
   "MakeExceptionEvent", MakeExceptionEvent,
   "MakeBreakEvent", MakeBreakEvent,
   "MakeCompileEvent", MakeCompileEvent,
   "MakeAsyncTaskEvent", MakeAsyncTaskEvent,
   "IsBreakPointTriggered", IsBreakPointTriggered,
 ]);
 
 })