Link to PDF file (or attach file here):
[pages4.pdf](https://github.com/mozilla/pdf.js/files/1128300/pages4.pdf)

Configuration:
- Web browser and its version: Firefox 54
- Operating system and its version: Win 10
- PDF.js version: 1.8.522
- Is an extension: no

What is the expected behavior? (add screenshot)
![chrome1-1 1](https://user-images.githubusercontent.com/146436/27918380-2f74512a-6245-11e7-8525-d0038fa6c2e8.jpg)
![chrome1-2 1](https://user-images.githubusercontent.com/146436/27918425-54f8e47e-6245-11e7-9bff-127f79ad0511.jpg)


What went wrong? (add screenshot)
![screenshot from 2017-07-06 12-10-30](https://user-images.githubusercontent.com/146436/27918442-5d57624e-6245-11e7-9436-5ba31cc8bd1a.png)
![screenshot from 2017-07-06 12-10-44](https://user-images.githubusercontent.com/146436/27918454-63b486da-6245-11e7-9eb5-c03aa5c40943.png)



if (this.current.resumeSMaskCtx) {
      this.resumeSMaskGroup();
    }
    
    
    if (
      this.current.activeSMask !== null &&
      (this.stateStack.length === 0 ||
        this.stateStack[this.stateStack.length - 1].activeSMask !==
          this.current.activeSMask)
    ) {
      this.endSMaskGroup();
    }
    if (this.stateStack.length !== 0) {
      this.current = this.stateStack.pop();
      this.ctx.restore();
      
      this.pendingClip = null;
      this._cachedGetSinglePixelWidth = null;
    } else {
      
      this.current.activeSMask = null;
    }
  }
  transform(a, b, c, d, e, f) {