Fix Symbol fonts without font file but with Encoding dictionary (issue 5238)
Implement streaming using moz-chunk-arraybuffer
Replaces (chunk in this.loadedChunks)
Moves watchScroll and getVisibleElements from PDFView
Moves thumbs logic into PDFThumbnailViewer.
Moves viewer code into PDFViewer and some code from PageView.
Moves pdfDocument.getPage/getTextContent requests out of PDFView
Moves rendering queue logic from PDFView
Removes PresentationMode dependency from PDFViewer
Removes any usage of PDFView in the PageView
Moves constants to avoid dependency on PDFView
Merge pull request #5263 from yurydelendik/stream

Implement streaming using moz-chunk-arraybuffer
Disables hash options when PDFBug is disabled and fixed streaming regressions.
Merge pull request #5346 from yurydelendik/streamfix

Misc follow ups on the streaming requests
Merge pull request #5250 from Snuffleupagus/issue-5238

Fix Symbol fonts without font file but with Encoding dictionary (issue 5238)
Use |toUnicode| when creating the glyph map for standard CIDFontType2 fonts without embedded font file
Marks some private methods in PDFViewer and PDFThumbnailViewer

Conflicts:
	web/pdf_viewer.js
Adds types definitions (jsdoc) for the PDFViewer code.
Renames and refactors PDFView to PDFViewerApplication.
Merge pull request #5295 from yurydelendik/pdfviewer

Refactoring to move page display code into separate class