[api-minor] Normalize the view-getter on the worker-thread

*Please note:* I don't really expect that this is will be an observable change, since virtually all PDF documents already order e.g. /MediaBox and /CropBox entries correctly.

By normalizing boundingBoxes already on the worker-thread, we can be sure that even a corrupt document won't cause issues.
Note how we're passing the `view`-getter to the `PartialEvaluator.getTextContent` method, in order to detect textContent which is outside of the page, hence it makes sense to ensure that it's formatted as expected.
Furthermore, by normalizing this once on the worker-tread we should no longer have to worry about a possibly negative width/height in the `PageViewport` constructor.

Finally, the patch also simplifies the `view`-getter a little bit.

src/core/document.js

@@ -146,12 +146,11 @@ class Page {
     if (this.xfaData) {
       return this.xfaData.bbox;
     }
-
     const box = this._getInheritableProperty(name, /* getArray = */ true);
 
     if (Array.isArray(box) && box.length === 4) {
       if (box[2] - box[0] !== 0 && box[3] - box[1] !== 0) {
-        return box;
+        return Util.normalizeRect(box);
       }
       warn(`Empty /${name} entry.`);
     }
@@ -190,18 +189,15 @@ class Page {
     // extend beyond the boundaries of the media box. If they do, they are
     // effectively reduced to their intersection with the media box."
     const { cropBox, mediaBox } = this;
-    let view;
-    if (cropBox === mediaBox || isArrayEqual(cropBox, mediaBox)) {
-      view = mediaBox;
-    } else {
+
+    if (cropBox !== mediaBox && !isArrayEqual(cropBox, mediaBox)) {
       const box = Util.intersect(cropBox, mediaBox);
       if (box && box[2] - box[0] !== 0 && box[3] - box[1] !== 0) {
-        view = box;
-      } else {
-        warn("Empty /CropBox and /MediaBox intersection.");
+        return shadow(this, "view", box);
       }
+      warn("Empty /CropBox and /MediaBox intersection.");
     }
-    return shadow(this, "view", view || mediaBox);
+    return shadow(this, "view", mediaBox);
   }
 
   get rotate() {

src/display/display_utils.js

@@ -224,13 +224,13 @@ class PageViewport {
     if (rotateA === 0) {
       offsetCanvasX = Math.abs(centerY - viewBox[1]) * scale + offsetX;
       offsetCanvasY = Math.abs(centerX - viewBox[0]) * scale + offsetY;
-      width = Math.abs(viewBox[3] - viewBox[1]) * scale;
-      height = Math.abs(viewBox[2] - viewBox[0]) * scale;
+      width = (viewBox[3] - viewBox[1]) * scale;
+      height = (viewBox[2] - viewBox[0]) * scale;
     } else {
       offsetCanvasX = Math.abs(centerX - viewBox[0]) * scale + offsetX;
       offsetCanvasY = Math.abs(centerY - viewBox[1]) * scale + offsetY;
-      width = Math.abs(viewBox[2] - viewBox[0]) * scale;
-      height = Math.abs(viewBox[3] - viewBox[1]) * scale;
+      width = (viewBox[2] - viewBox[0]) * scale;
+      height = (viewBox[3] - viewBox[1]) * scale;
     }
     // creating transform for the following operations:
     // translate(-centerX, -centerY), rotate and flip vertically,