Add a private API method to install a webstore app from Files.app

chrome/common/extensions/api/file_browser_private.json

Index: chrome/common/extensions/api/file_browser_private.json
diff --git a/chrome/common/extensions/api/file_browser_private.json b/chrome/common/extensions/api/file_browser_private.json
index 98fb729224ec85660984670e94cf192f1b20e66a..695f0fb93c1b85295cc11d2d0c95d3162f550ea9 100644
--- a/chrome/common/extensions/api/file_browser_private.json
+++ b/chrome/common/extensions/api/file_browser_private.json
@@ -1173,6 +1173,38 @@
             ]
           }
         ]
+      },
+      {
+        "name": "installWebstoreItem",
+        "type": "function",
+        "description": "Requests to install a webstore item.",
+        "parameters": [
+          {
+            "name": "item_id",
+            "type": "string",
+            "description": "The id of the item to install."
+          },
+          {
+            "name": "callback",
+            "type": "function",
+            "parameters": [
+              {
+                "type": "object",
+                "properties": {
+                  "result": {
+                    "type": "boolean",
+                    "description": "True if the item is installed. False if failed or aborted."
+                  },
+                  "error": {
+                    "type": "string",
+                    "optional": true,
+                    "description": "Reason of failure."
+                  }
+                }
+              }
+            ]
+          }
+        ]
       }
     ],
     "events": [