Make request save file return a pickedFile.

Previously the media app was unable to perform a save as operation on a
file obtained from a drag and drop or from a paste event. This was
because the logic surrounding the operation was encapsulated in
ReceivedFile which is a class the media app does not have access to.
This cl updates the requestSaveFile IPC to return a ReceivedFile
instead of returning a file token, allowing the media app to obtain a
native file, overwrite it and copy over it's functions so future saves
can happen in place.

The google3 side of this change is @ cl/334717684.

Bug: b/165769056, b/169630668
Change-Id: Ied8dd540f9f319b18b427e6566851bc628ed3204
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2439969Reviewed-by: Trent Apted <tapted@chromium.org>
Reviewed-by: dstockwell <dstockwell@google.com>
Commit-Queue: Zain Afzal <zafzal@google.com>
Cr-Commit-Position: refs/heads/master@{#812607}

chromeos/components/media_app_ui/resources/js/launch.js

@@ -245,7 +245,16 @@ guestMessagePipe.registerHandler(Message.REQUEST_SAVE_FILE, async (message) => {
       /** @type {!RequestSaveFileMessage} */ (message);
   const handle = await pickWritableFile(suggestedName, mimeType);
   /** @type {!RequestSaveFileResponse} */
-  const response = {token: generateToken(handle)};
+  const response = {
+    pickedFileContext: {
+      token: generateToken(handle),
+      file: assertCast(await handle.getFile()),
+      name: handle.name,
+      error: '',
+      canDelete: false,
+      canRename: false,
+    }
+  };
   return response;
 });
 

chromeos/components/media_app_ui/resources/js/media_app.externs.js

@@ -145,17 +145,17 @@ mediaApp.ClientApiDelegate = function() {};
 mediaApp.ClientApiDelegate.prototype.openFeedbackDialog = function() {};
 /**
  * Request for the user to be prompted with a save file dialog. Once the user
- * selects a location a new file handle is created and a unique token to that
- * file will be returned. This token can be then used with saveCopy(). The file
- * extension on `suggestedName` and the provided `mimeType` are used to inform
- * the save as dialog what file should be created. Once the Native Filesystem
- * API allows, this save as dialog will additionally have the filename input be
- * pre-filled with `suggestedName`.
+ * selects a location a new file handle is created and a new AbstractFile
+ * representing that file will be returned. This can be then used in a save as
+ * operation. The file extension on `suggestedName` and the provided `mimeType`
+ * are used to inform the save as dialog what file should be created. Once the
+ * Native Filesystem API allows, this save as dialog will additionally have the
+ * filename input be pre-filled with `suggestedName`.
  * TODO(b/161087799): Update function description once Native Filesystem API
  * supports suggestedName.
  * @param {string} suggestedName
  * @param {string} mimeType
- * @return {!Promise<number>}
+ * @return {!Promise<!mediaApp.AbstractFile>}
  */
 mediaApp.ClientApiDelegate.prototype.requestSaveFile = function(
     suggestedName, mimeType) {};

chromeos/components/media_app_ui/resources/js/message_types.js

@@ -140,7 +140,7 @@ let RequestSaveFileMessage;
  * Response message sent by the privileged context with a unique identifier for
  * the new writable file created on disk by the corresponding request save
  * file message.
- * @typedef {{token: number}}
+ * @typedef {{pickedFileContext: !FileContext}}
  */
 let RequestSaveFileResponse;
 

chromeos/components/media_app_ui/resources/js/receiver.js

@@ -223,7 +223,7 @@ const DELEGATE = {
   /**
    * @param {string} suggestedName
    * @param {string} mimeType
-   * @return {!Promise<number>}
+   * @return {!Promise<!mediaApp.AbstractFile>}
    */
   async requestSaveFile(suggestedName, mimeType) {
     /** @type {!RequestSaveFileMessage} */
@@ -232,7 +232,7 @@ const DELEGATE = {
         /** @type {!RequestSaveFileResponse} */ (
             await parentMessagePipe.sendMessage(
                 Message.REQUEST_SAVE_FILE, msg));
-    return response.token;
+    return new ReceivedFile(response.pickedFileContext);
   },
   /**
    * @return {!Promise<undefined>}

chromeos/components/media_app_ui/test/guest_query_receiver.js

@@ -98,9 +98,9 @@ async function runTestQuery(data) {
     if (!existingFile) {
       result = 'requestSaveFile failed, no file loaded';
     } else {
-      const token = await DELEGATE.requestSaveFile(
+      const pickedFile = await DELEGATE.requestSaveFile(
           existingFile.name, existingFile.mimeType);
-      result = token.toString();
+      result = assertCast(pickedFile.token).toString();
     }
   } else if (data.saveAs) {
     const existingFile = assertCast(lastReceivedFileList).item(0);
@@ -109,10 +109,11 @@ async function runTestQuery(data) {
     } else {
       const file = firstReceivedItem();
       try {
-        const token = await DELEGATE.requestSaveFile(
-            existingFile.name, existingFile.mimeType);
+        const token = (await DELEGATE.requestSaveFile(
+                           existingFile.name, existingFile.mimeType))
+                          .token;
         const testBlob = new Blob([data.saveAs]);
-        await assertCast(file.saveAs).call(file, testBlob, token);
+        await assertCast(file.saveAs).call(file, testBlob, assertCast(token));
         result = file.name;
         extraResultData = {blobText: await file.blob.text()};
       } catch (/** @type{!Error} */ error) {

chromeos/components/media_app_ui/test/media_app_ui_browsertest.js

@@ -922,6 +922,8 @@ TEST_F('MediaAppUIBrowserTest', 'RequestSaveFileIPC', async () => {
   const result = await sendTestMessage({requestSaveFile: true});
   const options = await chooseEntries;
   const lastToken = [...tokenMap.keys()].slice(-1)[0];
+  // Check the token matches to confirm the ReceivedFile returned represents the
+  // new file created on disk.
   assertMatch(result.testQueryResult, lastToken);
   assertEquals(options.types.length, 1);
   assertEquals(options.types[0].description, '.png');