diff --git a/toolkit/components/osfile/osfile_async_front.jsm b/toolkit/components/osfile/osfile_async_front.jsm
index 2ee584c226e..39ad18aecdc 100644
--- a/toolkit/components/osfile/osfile_async_front.jsm
+++ b/toolkit/components/osfile/osfile_async_front.jsm
@@ -240,37 +240,13 @@ File.prototype = {
    * @resolves {Uint8Array} An array containing the bytes read.
    */
   read: function read(nbytes) {
-    // FIXME: Once bug 720949 has landed, we might be able to simplify
-    // the implementation of |readAll|
-    let self = this;
-    let promise;
-    if (nbytes != null) {
-      promise = Promise.resolve(nbytes);
-    } else {
-      promise = this.stat();
-      promise = promise.then(function withStat(stat) {
-        return stat.size;
+    let promise = Scheduler.post("File_prototype_read",
+      [this._fdmsg,
+       nbytes]);
+    return promise.then(
+      function onSuccess(data) {
+        return new Uint8Array(data.buffer, data.byteOffset, data.byteLength);
       });
-    }
-    let array;
-    let size;
-    promise = promise.then(
-      function withSize(aSize) {
-        size = aSize;
-        array = new Uint8Array(size);
-        return self.readTo(array);
-      }
-    );
-    promise = promise.then(
-      function afterReadTo(bytes) {
-        if (bytes == size) {
-          return array;
-        } else {
-          return array.subarray(0, bytes);
-        }
-      }
-    );
-    return promise;
   },
 
   /**
@@ -475,8 +451,12 @@ File.makeDir = function makeDir(path, options) {
  * read from the file.
  */
 File.read = function read(path, bytes) {
-  return Scheduler.post("read",
+  let promise = Scheduler.post("read",
     [Type.path.toMsg(path), bytes], path);
+  return promise.then(
+    function onSuccess(data) {
+      return new Uint8Array(data.buffer, data.byteOffset, data.byteLength);
+    });
 };
 
 /**
diff --git a/toolkit/components/osfile/osfile_async_worker.js b/toolkit/components/osfile/osfile_async_worker.js
index 495fc4e8fe3..41c5609c28b 100644
--- a/toolkit/components/osfile/osfile_async_worker.js
+++ b/toolkit/components/osfile/osfile_async_worker.js
@@ -62,7 +62,12 @@ if (this.Components) {
          if (DEBUG) {
            LOG("Sending positive reply", JSON.stringify(result), "id is", id);
          }
-         self.postMessage({ok: result, id:id});
+         if (result instanceof Transfer) {
+           // Take advantage of zero-copy transfers
+           self.postMessage({ok: result.data, id: id}, result.transfers);
+         } else {
+           self.postMessage({ok: result, id:id});
+         }
        } else if (exn == StopIteration) {
          // StopIteration cannot be serialized automatically
          if (DEBUG) {
@@ -173,6 +178,21 @@ if (this.Components) {
 
      let File = exports.OS.File;
 
+     /**
+      * A constructor used to transfer data to the caller
+      * without copy.
+      *
+      * @param {*} data The data to return to the caller.
+      * @param {Array} transfers An array of Transferable
+      * values that should be moved instead of being copied.
+      *
+      * @constructor
+      */
+     let Transfer = function Transfer(data, transfers) {
+       this.data = data;
+       this.transfers = transfers;
+     };
+
      /**
       * The agent.
       *
@@ -214,7 +234,8 @@ if (this.Components) {
          return OpenedFiles.add(file);
        },
        read: function read(path, bytes) {
-         return File.read(Type.path.fromMsg(path), bytes);
+         let data = File.read(Type.path.fromMsg(path), bytes);
+         return new Transfer({buffer: data.buffer, byteOffset: data.byteOffset, byteLength: data.byteLength}, [data.buffer]);
        },
        exists: function exists(path) {
          return File.exists(Type.path.fromMsg(path));
@@ -249,6 +270,14 @@ if (this.Components) {
              return exports.OS.File.Info.toMsg(this.stat());
            });
        },
+       File_prototype_read: function read(fd, nbytes, options) {
+         return withFile(fd,
+           function do_read() {
+             let data = this.read(nbytes, options);
+             return new Transfer({buffer: data.buffer, byteOffset: data.byteOffset, byteLength: data.byteLength}, [data.buffer]);
+           }
+         );
+       },
        File_prototype_readTo: function readTo(fd, buffer, options) {
          return withFile(fd,
            function do_readTo() {