[piexwasm] Make callers handle Piex Module failure

piex-wasm assumes chrome.runtime.reload can be used to reload the page
on Module failures. Other environments (normal web pages, web workers,
NodeJS, etc) obviously can't use chrome.runtime.reload.

Remove the chrome.runtime.reload assumption: change the client code to
provide the failure handler to piex-wasm. Change image_request_task.js
RAW image client code: pass in the chrome.runtime.reload handler.

While here, add or adjust comments to image_request_task.js and change
the direct loading case to arrow function. No change in behavior.

Bug: 1132695
No-try: true
Change-Id: I6a2b641cdc036dd208f4d64deb4f0b7fdff0835f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2432705
Commit-Queue: Noel Gordon <noel@chromium.org>
Reviewed-by: Trent Apted <tapted@chromium.org>
Cr-Commit-Position: refs/heads/master@{#811085}

ui/file_manager/image_loader/image_request_task.js

@@ -287,13 +287,16 @@ ImageRequestTask.prototype.getExternalThumbnail = function(url, onFailure) {
 };
 
 /**
- * Downloads an image directly or for remote resources using the XmlHttpRequest.
+ * Loads |this.image_| with the |this.request_.url| source or the thumbnail
+ * image of the source.
  *
  * @param {function()} onSuccess Success callback.
  * @param {function()} onFailure Failure callback.
  * @private
  */
 ImageRequestTask.prototype.downloadOriginal_ = function(onSuccess, onFailure) {
+  // Load methods below set |this.image_.src|. Call revokeObjectURL(src) to
+  // release resources if the image src was created with createObjectURL().
   this.image_.onload = function() {
     URL.revokeObjectURL(this.image_.src);
     onSuccess();
@@ -303,18 +306,22 @@ ImageRequestTask.prototype.downloadOriginal_ = function(onSuccess, onFailure) {
     onFailure();
   }.bind(this);
 
-  // Download data urls directly since they are not supported by XmlHttpRequest.
+  // Load dataURL sources directly.
   const dataUrlMatches = this.request_.url.match(/^data:([^,;]*)[,;]/);
   if (dataUrlMatches) {
     this.image_.src = this.request_.url;
     this.contentType_ = dataUrlMatches[1];
     return;
   }
+
+  // Load Drive source thumbnail.
   const drivefsUrlMatches = this.request_.url.match(/^drivefs:(.*)/);
   if (drivefsUrlMatches) {
     this.getExternalThumbnail(drivefsUrlMatches[1], onFailure);
     return;
   }
+
+  // Load PDF source thumbnail.
   if (this.request_.url.endsWith('.pdf')) {
     this.getExternalThumbnail(this.request_.url, onFailure);
     return;
@@ -322,9 +329,9 @@ ImageRequestTask.prototype.downloadOriginal_ = function(onSuccess, onFailure) {
 
   const fileType = FileType.getTypeForName(this.request_.url);
 
-  // Load RAW images by using Piex loader instead of XHR.
+  // Load RAW image source thumbnail.
   if (fileType.type === 'raw') {
-    this.piexLoader_.load(this.request_.url)
+    this.piexLoader_.load(this.request_.url, chrome.runtime.reload)
         .then(
             function(data) {
               this.request_.orientation = data.orientation;
@@ -335,13 +342,13 @@ ImageRequestTask.prototype.downloadOriginal_ = function(onSuccess, onFailure) {
               this.image_.src = URL.createObjectURL(blob);
             }.bind(this),
             function() {
-              // The error has already been logged in PiexLoader.
+              // PiexLoader calls console.error on errors.
               onFailure();
             });
     return;
   }
 
-  // Load video thumbnails by using video tag instead of XHR.
+  // Load video source thumbnail.
   if (fileType.type === 'video') {
     this.createVideoThumbnailUrl_(this.request_.url)
         .then(function(url) {
@@ -354,16 +361,11 @@ ImageRequestTask.prototype.downloadOriginal_ = function(onSuccess, onFailure) {
     return;
   }
 
-  // Fetch the image via XHR and parse it.
-  const parseImage = function(contentType, blob) {
-    if (contentType) {
-      this.contentType_ = contentType;
-    }
-    this.image_.src = URL.createObjectURL(blob);
-  }.bind(this);
-
-  // Request raw data via XHR.
-  this.load(this.request_.url, parseImage, onFailure);
+  // Load the source directly.
+  this.load(this.request_.url, (contentType, blob) => {
+    this.image_.src = blob ? URL.createObjectURL(blob) : '!';
+    this.contentType_ = contentType || null;
+  }, onFailure);
 };
 
 /**

ui/file_manager/image_loader/piex_loader.js

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-console.log('[PiexLoader] wasm mode loaded');
+console.log('[PiexLoader] loaded');
 
 /**
  * Declares the piex-wasm Module interface. The Module has many interfaces
@@ -25,33 +25,33 @@ let PiexWasmModule;
 const PiexModule = window['Module'] || {};
 
 /**
- * Set true only if the wasm Module.onAbort() handler is called.
+ * Set true only if the Module.onAbort() handler is called.
  * @type {boolean}
  */
-let wasmFailed = false;
+let piexFailed = false;
 
 /**
- * Installs an (Emscripten) wasm Module.onAbort handler, that records that
- * the Module has failed and re-throws the error.
+ * Installs an (Emscripten) Module.onAbort handler. Record that the Module
+ * has failed and re-throw the error.
  * @throws {!Error|string}
  */
 PiexModule.onAbort = (error) => {
-  wasmFailed = true;
+  piexFailed = true;
   throw error;
 };
 
 /**
- * Module failure recovery: if wasmFailed is set via onAbort due to OOM in
+ * Module failure recovery: if piexFailed is set via onAbort due to OOM in
  * the C++ for example, or the Module failed to load or call run, then the
- * wasm Module is in a broken, non-functional state.
+ * Module is in a broken, non-functional state.
  *
- * Re-loading the page is the only reliable way to attempt to recover from
- * broken Module state.
+ * Loading the entire page is the only reliable way to recover from broken
+ * Module state. Log the error, and return true to tell caller to initiate
+ * failure recovery steps.
  */
-function wasmModuleFailed() {
-  if (wasmFailed || !PiexModule.calledRun) {
-    console.error('[PiexLoader] wasmModuleFailed');
-    setTimeout(chrome.runtime.reload, 0);
+function piexModuleFailed() {
+  if (piexFailed || !PiexModule.calledRun) {
+    console.error('[PiexLoader] piex wasm module failed');
     return true;
   }
 }
@@ -106,15 +106,6 @@ function PiexLoaderResponse(data) {
   this.ifd = data.ifd || null;
 }
 
-/**
- * Creates a PiexLoader for reading RAW image file information.
- * @constructor
- * @struct
- */
-function PiexLoader() {
-  // TODO(crbug.com/1039141): make this an ES6 class.
-}
-
 /**
  * Resolves the file entry associated with DOM filesystem |url| and returns
  * the file content in an ArrayBuffer.
@@ -468,16 +459,32 @@ class ImageBuffer {
 }
 
 /**
- * Starts to load RAW image.
+ * Creates a PiexLoader.
+ * @constructor
+ * @struct
+ */
+function PiexLoader() {}
+
+/**
+ * Loads a RAW image. Returns the image metadata and the image thumbnail in a
+ * PiexLoaderResponse.
+ *
+ * piexModuleFailed() returns true if the Module is in an unrecoverable error
+ * state. This is rare, but possible, and the only reliable way to recover is
+ * to reload the page. Callback |onPiexModuleFailed| is used to indicate that
+ * the caller should initiate failure recovery steps.
+ *
  * @param {string} url
+ * @param {!function()} onPiexModuleFailed
  * @return {!Promise<!PiexLoaderResponse>}
  */
-PiexLoader.prototype.load = function(url) {
+PiexLoader.prototype.load = function(url, onPiexModuleFailed) {
   let imageBuffer;
 
   return readFromFileSystem(url)
       .then((buffer) => {
-        if (wasmModuleFailed() === true) {
+        if (piexModuleFailed() === true) {
+          // Just reject here: handle in the .catch() clause below.
           return Promise.reject('piex wasm module failed');
         }
         imageBuffer = new ImageBuffer(buffer);
@@ -488,7 +495,8 @@ PiexLoader.prototype.load = function(url) {
         return new PiexLoaderResponse(imageBuffer.preview(result));
       })
       .catch((error) => {
-        if (wasmModuleFailed() === true) {
+        if (piexModuleFailed() === true) {
+          setTimeout(onPiexModuleFailed, 0);
           return Promise.reject('piex wasm module failed');
         }
         imageBuffer && imageBuffer.close();