Reset `pageRotation` and `downloadComplete` in `PDFViewerApplication.close`

Currently, these properties are reset in what appears to be somewhat arbitrary locations (within the `load` and `open` methods respectively). The explanation is probably that both of these properties predates the existence of any centralized clean-up code in the viewer.

Hence I think that it makes sense to move the resetting of these properties to the `close` method, since that improves the overview of what's actually cleaned-up/reset when changing documents in the viewer.

web/app.js

@@ -136,6 +136,7 @@ var PDFViewerApplication = {
   l10n: null,
   pageRotation: 0,
   isInitialViewSet: false,
+  downloadComplete: false,
   viewerPrefs: {
     sidebarViewOnLoad: SidebarView.NONE,
     pdfBugEnabled: false,
@@ -599,7 +600,9 @@ var PDFViewerApplication = {
       this.pdfDocumentProperties.setDocument(null, null);
     }
     this.store = null;
+    this.pageRotation = 0;
     this.isInitialViewSet = false;
+    this.downloadComplete = false;
 
     this.pdfSidebar.reset();
     this.pdfOutlineViewer.reset();
@@ -669,8 +672,6 @@ var PDFViewerApplication = {
       }
     }
 
-    this.downloadComplete = false;
-
     let loadingTask = getDocument(parameters);
     this.pdfLoadingTask = loadingTask;
 
@@ -911,8 +912,6 @@ var PDFViewerApplication = {
     let pagesPromise = pdfViewer.pagesPromise;
     let onePageRendered = pdfViewer.onePageRendered;
 
-    this.pageRotation = 0;
-
     let pdfThumbnailViewer = this.pdfThumbnailViewer;
     pdfThumbnailViewer.setDocument(pdfDocument);
 
@@ -1241,8 +1240,11 @@ var PDFViewerApplication = {
     this.forceRendering();
   },
 
-  rotatePages: function pdfViewRotatePages(delta) {
+  rotatePages(delta) {
-    var pageNumber = this.page;
+    if (!this.pdfDocument) {
+      return;
+    }
+    let pageNumber = this.page;
     this.pageRotation = (this.pageRotation + 360 + delta) % 360;
     this.pdfViewer.pagesRotation = this.pageRotation;
     this.pdfThumbnailViewer.pagesRotation = this.pageRotation;