[fsp] Add requestUnmount() method together with the request manager.

chrome/renderer/resources/extensions/file_system_provider_custom_bindings.js

Index: chrome/renderer/resources/extensions/file_system_provider_custom_bindings.js
diff --git a/chrome/renderer/resources/extensions/file_system_provider_custom_bindings.js b/chrome/renderer/resources/extensions/file_system_provider_custom_bindings.js
index b7e2ea8548b001aa2dc990fa4c4d51137ad5ba61..b89613808ab7431511ec8dc49f9163a50308f710 100644
--- a/chrome/renderer/resources/extensions/file_system_provider_custom_bindings.js
+++ b/chrome/renderer/resources/extensions/file_system_provider_custom_bindings.js
@@ -5,6 +5,9 @@
 // Custom binding for the fileSystemProvider API.
 
 var binding = require('binding').Binding.create('fileSystemProvider');
+var fileSystemProviderInternal =
+    require('binding').Binding.create('fileSystemProviderInternal').generate();
+var eventBindings = require('event_bindings');
 var fileSystemNatives = requireNative('file_system_natives');
 var GetDOMError = fileSystemNatives.GetDOMError;
 
@@ -44,6 +47,54 @@ binding.registerCustomHook(function(bindingsAPI) {
           successCallback(fileSystemId);
       }
     });
+
+  apiFunctions.setUpdateArgumentsPostValidate(
+    'unmount',
+    function(fileSystemId, successCallback, errorCallback) {
+      // Piggyback the error callback onto the success callback,
+      // so we can use the error callback later.
+      successCallback.errorCallback_ = errorCallback;
+      return [fileSystemId, successCallback];
+    });
+
+  apiFunctions.setCustomCallback(
+    'unmount',
+    function(name, request, response) {
+      var domError = null;
+      if (request.callback) {
+        // DOMError is present only if mount() failed.
+        if (response && response[0]) {
+          // Convert a Dictionary to a DOMError.
+          domError = GetDOMError(response[0].name, response[0].message);
+          response.length = 1;
+        }
+
+        var successCallback = request.callback;
+        var errorCallback = request.callback.errorCallback_;
+        delete request.callback;
+
+        if (domError)
+          errorCallback(domError);
+        else
+          successCallback();
+      }
+    });
 });
 
+eventBindings.registerArgumentMassager(
+    'fileSystemProvider.onUnmountRequested',
+    function(args, dispatch) {
+      var fileSystemId = args[0];
+      var requestId = args[1];
+      var onSuccessCallback = function() {
+        fileSystemProviderInternal.unmountRequestedSuccess(
+            fileSystemId, requestId);
+      };
+      var onErrorCallback = function(error) {
+        fileSystemProviderInternal.unmountRequestedError(
+          fileSystemId, requestId, error);
+      }
+      dispatch([fileSystemId, onSuccessCallback, onErrorCallback]);
+    });
+
 exports.binding = binding.generate();