**Link to PDF file (or attach file here):**
[tocheckFile.pdf](https://github.com/mozilla/pdf.js/files/240714/tocheckFile.pdf)

**Configuration:**
- Web browser and its version: FF45.0.2, Chrome Version 50.0.2661.86 (64-bit) 
- Operating system and its version: Mac OSX El Capitan

**\- PDF.js version:**
PDFJS.version = '1.1.215';
PDFJS.build = 'c9a7498';

**Steps to reproduce the problem:**
1. Use the lib to generate a PDF preview.

**What is the expected behavior? (add screenshot)**
PDF preview should have rendered completely. (frog head should be complete)

**What went wrong? (add screenshot)**
<img width="952" alt="imagesnotrenderinginpreview" src="https://cloud.githubusercontent.com/assets/10231850/14889265/cecb2d64-0d66-11e6-98e1-da2d39728552.png">

See attached screenshot in regards to the pdf file

Link to a viewer (if hosted on a site other than mozilla.github.io/pdf.js or as Firefox/Chrome extension):

const activeSMask = this.current.activeSMask;
    const drawnWidth = activeSMask.canvas.width;
    const drawnHeight = activeSMask.canvas.height;
    const cacheId = "smaskGroupAt" + this.groupLevel;
    const scratchCanvas = this.cachedCanvases.getCanvas(
      cacheId,
      drawnWidth,
      drawnHeight,
      true
    );
    const currentCtx = this.ctx;
    const currentTransform = currentCtx.mozCurrentTransform;
    this.ctx.save();
    const groupCtx = scratchCanvas.context;
    groupCtx.scale(1 / activeSMask.scaleX, 1 / activeSMask.scaleY);
    groupCtx.translate(-activeSMask.offsetX, -activeSMask.offsetY);
    groupCtx.transform.apply(groupCtx, currentTransform);
    activeSMask.startTransformInverse = groupCtx.mozCurrentTransformInverse;
    copyCtxState(currentCtx, groupCtx);
    this.ctx = groupCtx;
    this.setGState([
      ["BM", "source-over"],
      ["ca", 1],
      ["CA", 1],
    ]);
    this.groupStack.push(currentCtx);
    this.groupLevel++;
  }
  suspendSMaskGroup() {