[DevTools] Add dialog type and return value to Page.javascriptDialog{Opening,Closed}.

Source/devtools/protocol.json

 {
     "version": { "major": "1", "minor": "1" },
     "domains": [{
         "domain": "Inspector",
         "hidden": true,
         "types": [],
         "commands": [
             {
                 "name": "enable",
                 "description": "Enables inspector domain notifications.",
@@ skipping 124 matching lines @@
                 "properties": [
                     { "name": "offsetTop", "type": "number", "hidden": true, "description": "Top offset in DIP." },
                     { "name": "pageScaleFactor", "type": "number", "hidden": true, "description": "Page scale factor." },
                     { "name": "deviceWidth", "type": "number", "hidden": true, "description": "Device screen width in DIP." },
                     { "name": "deviceHeight", "type": "number", "hidden": true, "description": "Device screen height in DIP." },
                     { "name": "scrollOffsetX", "type": "number", "hidden": true, "description": "Position of horizontal scroll in CSS pixels." },
                     { "name": "scrollOffsetY", "type": "number", "hidden": true, "description": "Position of vertical scroll in CSS pixels." },
                     { "name": "timestamp", "type": "number", "optional": true, "hidden": true, "description": "Frame swap timestamp." }
                 ],
                 "hidden": true
+            },
+            {
+                "id": "DialogType",
+                "description": "Javascript dialog type",
+                "type": "string",
+                "enum": ["alert", "confirm", "prompt", "beforeunload"],
+                "hidden": true
             }
         ],
         "commands": [
             {
                 "name": "enable",
                 "description": "Enables page domain notifications.",
                 "handlers": ["browser", "renderer"]
             },
             {
                 "name": "disable",
@@ skipping 348 matching lines @@
                 "hidden": true
             },
             {
                 "name": "frameResized",
                 "hidden": true
             },
             {
                 "name": "javascriptDialogOpening",
                 "description": "Fired when a JavaScript initiated dialog (alert, confirm, prompt, or onbeforeunload) is about to open.",
                 "parameters": [
-                    { "name": "message", "type": "string", "description": "Message that will be displayed by the dialog." }
+                    { "name": "message", "type": "string", "description": "Message that will be displayed by the dialog." },
+                    { "name": "type", "$ref": "DialogType", "description": "Dialog type." }
                 ],
                 "hidden": true
             },
             {
                 "name": "javascriptDialogClosed",
                 "description": "Fired when a JavaScript initiated dialog (alert, confirm, prompt, or onbeforeunload) has been closed.",
+                "parameters": [
+                    { "name": "result", "type": "boolean", "description": "Whether dialog was confirmed." }
+                ],
                 "hidden": true
             },
             {
                 "name": "screencastFrame",
                 "description": "Compressed image data requested by the <code>startScreencast</code>.",
                 "parameters": [
                     { "name": "data", "type": "string", "description": "Base64-encoded compressed image." },
                     { "name": "metadata", "$ref": "ScreencastFrameMetadata", "description": "Screencast frame metadata."},
                     { "name": "frameNumber", "type": "integer", "optional": true, "description": "Frame number."}
                 ],
@@ skipping 4488 matching lines @@
                 "name": "securityStateChanged",
                 "description": "The security state of the page changed.",
                 "parameters": [
                     { "name": "securityState", "$ref": "SecurityState", "description": "Security state." }
                 ],
                 "handlers": ["browser"]
             }
         ]
     }]
 }