[Firefox regression] Fix disableRange=true bug in PDFDataTransportStream

Currently if trying to set `disableRange=true` in the built-in PDF Viewer in Firefox, either through `about:config` or via the URL hash, the PDF document will never load. It appears that this has been broken for a couple of years, without anyone noticing.

Obviously it's not a good idea to set `disableRange=true`, however it seems that this bug affects the PDF Viewer in Firefox even with default settings:
 - In the case where `initialData` already contains the *entire* file, we're forced to dispatch a range request to re-fetch already available data just so that file loading may complete.
 - (In the case where the data arrives, via streaming, before being specifically requested through `requestDataRange`, we're also forced to re-fetch data unnecessarily.) *This part was removed, to reduce the scope/risk of the patch somewhat.*

In the cases outlined above, we're having to re-fetch already available data thus potentially delaying loading/rendering of PDF files in Firefox (and wasting resources in the process).

src/display/api.js

@@ -344,6 +344,7 @@ function getDocument(src) {
         networkStream = new PDFDataTransportStream({
           length: params.length,
           initialData: params.initialData,
+          progressiveDone: params.progressiveDone,
           disableRange: params.disableRange,
           disableStream: params.disableStream,
         }, rangeTransport);
@@ -389,6 +390,7 @@ function _fetchDocument(worker, source, pdfDataRangeTransport, docId) {
   if (pdfDataRangeTransport) {
     source.length = pdfDataRangeTransport.length;
     source.initialData = pdfDataRangeTransport.initialData;
+    source.progressiveDone = pdfDataRangeTransport.progressiveDone;
   }
   return worker.messageHandler.sendWithPromise('GetDocRequest', {
     docId,
@@ -515,13 +517,15 @@ const PDFDocumentLoadingTask = (function PDFDocumentLoadingTaskClosure() {
  * @param {Uint8Array} initialData
  */
 class PDFDataRangeTransport {
-  constructor(length, initialData) {
+  constructor(length, initialData, progressiveDone = false) {
     this.length = length;
     this.initialData = initialData;
+    this.progressiveDone = progressiveDone;
 
     this._rangeListeners = [];
     this._progressListeners = [];
     this._progressiveReadListeners = [];
+    this._progressiveDoneListeners = [];
     this._readyCapability = createPromiseCapability();
   }
 
@@ -537,6 +541,10 @@ class PDFDataRangeTransport {
     this._progressiveReadListeners.push(listener);
   }
 
+  addProgressiveDoneListener(listener) {
+    this._progressiveDoneListeners.push(listener);
+  }
+
   onDataRange(begin, chunk) {
     for (const listener of this._rangeListeners) {
       listener(begin, chunk);
@@ -559,6 +567,14 @@ class PDFDataRangeTransport {
     });
   }
 
+  onDataProgressiveDone() {
+    this._readyCapability.promise.then(() => {
+      for (const listener of this._progressiveDoneListeners) {
+        listener();
+      }
+    });
+  }
+
   transportReady() {
     this._readyCapability.resolve();
   }

src/display/transport_stream.js

@@ -21,7 +21,9 @@ var PDFDataTransportStream = (function PDFDataTransportStreamClosure() {
     assert(pdfDataRangeTransport);
 
     this._queuedChunks = [];
-    var initialData = params.initialData;
+    this._progressiveDone = params.progressiveDone || false;
+
+    const initialData = params.initialData;
     if (initialData && initialData.length > 0) {
       let buffer = new Uint8Array(initialData).buffer;
       this._queuedChunks.push(buffer);
@@ -47,6 +49,10 @@ var PDFDataTransportStream = (function PDFDataTransportStreamClosure() {
       this._onReceiveData({ chunk, });
     });
 
+    this._pdfDataRangeTransport.addProgressiveDoneListener(() => {
+      this._onProgressiveDone();
+    });
+
     this._pdfDataRangeTransport.transportReady();
   }
   PDFDataTransportStream.prototype = {
@@ -80,6 +86,13 @@ var PDFDataTransportStream = (function PDFDataTransportStreamClosure() {
        }
     },
 
+    _onProgressiveDone() {
+      if (this._fullRequestReader) {
+        this._fullRequestReader.progressiveDone();
+      }
+      this._progressiveDone = true;
+    },
+
     _removeRangeReader:
         function PDFDataTransportStream_removeRangeReader(reader) {
       var i = this._rangeReaders.indexOf(reader);
@@ -92,7 +105,8 @@ var PDFDataTransportStream = (function PDFDataTransportStreamClosure() {
       assert(!this._fullRequestReader);
       var queuedChunks = this._queuedChunks;
       this._queuedChunks = null;
-      return new PDFDataTransportStreamReader(this, queuedChunks);
+      return new PDFDataTransportStreamReader(this, queuedChunks,
+                                              this._progressiveDone);
     },
 
     getRangeReader: function PDFDataTransportStream_getRangeReader(begin, end) {
@@ -116,9 +130,10 @@ var PDFDataTransportStream = (function PDFDataTransportStreamClosure() {
   };
 
   /** @implements {IPDFStreamReader} */
-  function PDFDataTransportStreamReader(stream, queuedChunks) {
+  function PDFDataTransportStreamReader(stream, queuedChunks,
+                                        progressiveDone = false) {
     this._stream = stream;
-    this._done = false;
+    this._done = progressiveDone || false;
     this._filename = null;
     this._queuedChunks = queuedChunks || [];
     this._requests = [];
@@ -180,6 +195,13 @@ var PDFDataTransportStream = (function PDFDataTransportStreamClosure() {
       });
       this._requests = [];
     },
+
+    progressiveDone() {
+      if (this._done) {
+        return;
+      }
+      this._done = true;
+    },
   };
 
   /** @implements {IPDFStreamRangeReader} */