[api-minor] Refactor/simplify the PDFObject class

First of all, note how there's currently *two* methods for checking if a certain object exists, which seems completely unwarranted.
Furthermore, the rarely used `getData` method was removed and its only callsite changed to use a combination of `PDFObjects.{has, get}` instead.
Finally, the methods were rearranged slightly, to bring the most important ones (for an API user) to the top of the class.

src/display/annotation_layer.js

@@ -447,8 +447,9 @@ class TextWidgetAnnotationElement extends WidgetAnnotationElement {
  element.style.display = 'table-cell';
 
  let font = null;
- if (this.data.fontRefName) {
- font = this.page.commonObjs.getData(this.data.fontRefName);
+ if (this.data.fontRefName &&
+ this.page.commonObjs.has(this.data.fontRefName)) {
+ font = this.page.commonObjs.get(this.data.fontRefName);
  }
  this._setTextStyle(element, font);
  }

src/display/api.js

@@ -1885,7 +1885,7 @@ class WorkerTransport {
  }
 
  const [id, type, exportedData] = data;
- if (this.commonObjs.hasData(id)) {
+ if (this.commonObjs.has(id)) {
  return;
  }
 
@@ -1937,7 +1937,7 @@ class WorkerTransport {
 
  const [id, pageIndex, type, imageData] = data;
  const pageProxy = this.pageCache[pageIndex];
- if (pageProxy.objs.hasData(id)) {
+ if (pageProxy.objs.has(id)) {
  return;
  }
 
@@ -2256,6 +2256,11 @@ class PDFObjects {
  return obj.data;
  }
 
+ has(objId) {
+ const obj = this._objs[objId];
+ return (obj ? obj.resolved : false);
+ }
+
  /**
  * Resolves the object `objId` with optional `data`.
  */
@@ -2267,26 +2272,6 @@ class PDFObjects {
  obj.capability.resolve(data);
  }
 
- isResolved(objId) {
- const obj = this._objs[objId];
- return (obj ? obj.resolved : false);
- }
-
- hasData(objId) {
- return this.isResolved(objId);
- }
-
- /**
- * Returns the data of `objId` if the object exists, null otherwise.
- */
- getData(objId) {
- const obj = this._objs[objId];
- if (!obj || !obj.resolved) {
- return null;
- }
- return obj.data;
- }
-
  clear() {
  this._objs = Object.create(null);
  }

src/display/canvas.js

@@ -810,7 +810,7 @@ var CanvasGraphics = (function CanvasGraphicsClosure() {
 
  // If the promise isn't resolved yet, add the continueCallback
  // to the promise and bail out.
- if (!objsPool.isResolved(depObjId)) {
+ if (!objsPool.has(depObjId)) {
  objsPool.get(depObjId, continueCallback);
  return i;
  }