[debugger] expose side-effect free evaluate to inspector.

src/inspector/debugger_script_externs.js

Index: src/inspector/debugger_script_externs.js
diff --git a/src/inspector/debugger_script_externs.js b/src/inspector/debugger_script_externs.js
index 80eb864f85033f2d7a87d98218bc7f816c3361fb..93c9231e64a269aecd334c1f212769957b9d3bb4 100644
--- a/src/inspector/debugger_script_externs.js
+++ b/src/inspector/debugger_script_externs.js
@@ -31,7 +31,7 @@ var JavaScriptCallFrameDetails;
 /** @typedef {{
         contextId: function():number,
         thisObject: !Object,
-        evaluate: function(string):*,
+        evaluate: function(string, boolean):*,
         restart: function():undefined,
         setVariableValue: function(number, string, *):undefined,
         isAtReturn: boolean,
@@ -410,8 +410,9 @@ FrameMirror.prototype.script = function() {}
 
 /**
  * @param {string} source
+ * @param {boolean} allowSideEffect
  */
-FrameMirror.prototype.evaluate = function(source) {}
+FrameMirror.prototype.evaluate = function(source, allowSideEffect) {}
 
 FrameMirror.prototype.restart = function() {}