Import chrome idl into third_party

third_party/chrome/idl/page_capture.json

+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+[
+  {
+    "namespace": "pageCapture",
+    "functions": [
+      {
+        "name": "saveAsMHTML",
+        "type": "function",
+        "description": "Saves the content of the tab with given id as MHTML.",
+        "parameters": [
+          {
+            "name": "details",
+            "type": "object",
+            "properties": {
+              "tabId": {
+                "type": "integer",
+                "minimum": 0,
+                "description": "The id of the tab to save as MHTML."
+              }
+            }
+          },
+          {
+            "name": "callback",
+            "type": "function",
+            "description": "Called when the MHTML has been generated.",
+            "parameters": [
+              {
+                "name": "mhtmlData",
+                "type": "binary",
+                "optional": "true",
+                "description": "The MHTML data as a Blob."
+              }
+            ]
+          }
+        ]
+      }
+    ]
+  }
+]