I was wondering if WebGL is considered stable enough to be enabled by default. It makes some PDFs render much faster and it has been off by default for a while now, so we have had quite some time to test it.

If we decide to enable WebGL by default, we should not forget to update https://github.com/mozilla/pdf.js/blob/master/extensions/chromium/preferences_schema.json#L39 as well.

/cc @yurydelendik 
/cc @Snuffleupagus (because IIRC you were testing WebGL too)

this.pendingEOFill = false;
      this.res = null;
      this.xobjs = null;
      this.commonObjs = commonObjs;
      this.objs = objs;
      this.canvasFactory = canvasFactory;
      this.webGLContext = webGLContext;
      this.imageLayer = imageLayer;
      this.groupStack = [];
      this.processingType3 = null;
      
      
      this.baseTransform = null;
      this.baseTransformStack = [];
      this.groupLevel = 0;
      this.smaskStack = [];
      this.smaskCounter = 0;
      this.tempSMask = null;
      this.contentVisible = true;
      this.markedContentStack = [];
      this.optionalContentConfig = optionalContentConfig;
      this.cachedCanvases = new CachedCanvases(this.canvasFactory);
      if (canvasCtx) {
        
        
        addContextCurrentTransform(canvasCtx);
      }
      this._cachedGetSinglePixelWidth = null;
    }
    beginDrawing({