Remove the unused inline parameter from various methods/functions in PDFImage, and change a couple of methods to use Objects rather than plain parameters

The `inline` parameter is passed to a number of methods/functions in `PDFImage`, despite not actually being used. Its value is never checked, nor is it ever assigned to the current `PDFImage` instance (i.e. no `this.inline = inline` exists).
Looking briefly at the history of this code, I was also unable to find a point in time where `inline` was being used.

As far as I'm concerned, `inline` does nothing more than add clutter to already very unwieldy method/function signatures, hence why I'm proposing that we just remove it.
To further simplify call-sites using `PDFImage`/`NativeImageDecoder`, a number of methods/functions are changed to take Objects rather than a bunch of (somewhat) randomly ordered parameters.

src/core/image.js

@@ -74,7 +74,8 @@ var PDFImage = (function PDFImageClosure() {
     return dest;
   }
 
-  function PDFImage(xref, res, image, inline, smask, mask, isMask) {
+  function PDFImage({ xref, res, image, smask = null, mask = null,
+                      isMask = false, }) {
     this.image = image;
     var dict = image.dict;
     if (dict.has('Filter')) {
@@ -160,14 +161,23 @@ var PDFImage = (function PDFImageClosure() {
     }
 
     if (smask) {
-      this.smask = new PDFImage(xref, res, smask, false);
+      this.smask = new PDFImage({
+        xref,
+        res,
+        image: smask,
+      });
     } else if (mask) {
       if (isStream(mask)) {
         var maskDict = mask.dict, imageMask = maskDict.get('ImageMask', 'IM');
         if (!imageMask) {
           warn('Ignoring /Mask in image without /ImageMask.');
         } else {
-          this.mask = new PDFImage(xref, res, mask, false, null, null, true);
+          this.mask = new PDFImage({
+            xref,
+            res,
+            image: mask,
+            isMask: true,
+          });
         }
       } else {
         // Color key mask (just an array).
@@ -179,9 +189,8 @@ var PDFImage = (function PDFImageClosure() {
    * Handles processing of image data and returns the Promise that is resolved
    * with a PDFImage when the image is ready to be used.
    */
-  PDFImage.buildImage = function PDFImage_buildImage(handler, xref,
-                                                     res, image, inline,
-                                                     nativeDecoder) {
+  PDFImage.buildImage = function({ handler, xref, res, image,
+                                   nativeDecoder = null, }) {
     var imagePromise = handleImageData(image, nativeDecoder);
     var smaskPromise;
     var maskPromise;
@@ -208,17 +217,19 @@ var PDFImage = (function PDFImageClosure() {
       }
     }
     return Promise.all([imagePromise, smaskPromise, maskPromise]).then(
-      function(results) {
-        var imageData = results[0];
-        var smaskData = results[1];
-        var maskData = results[2];
-        return new PDFImage(xref, res, imageData, inline, smaskData, maskData);
+      function([imageData, smaskData, maskData]) {
+        return new PDFImage({
+          xref,
+          res,
+          image: imageData,
+          smask: smaskData,
+          mask: maskData,
+        });
       });
   };
 
-  PDFImage.createMask =
-      function PDFImage_createMask(imgArray, width, height,
-                                   imageIsFromDecodeStream, inverseDecode) {
+  PDFImage.createMask = function({ imgArray, width, height,
+                                   imageIsFromDecodeStream, inverseDecode, }) {
 
     // |imgArray| might not contain full data for every pixel of the mask, so
     // we need to distinguish between |computedLength| and |actualLength|.
@@ -271,7 +282,7 @@ var PDFImage = (function PDFImageClosure() {
                       this.mask && this.mask.height || 0);
     },
 
-    decodeBuffer: function PDFImage_decodeBuffer(buffer) {
+    decodeBuffer(buffer) {
       var bpc = this.bpc;
       var numComps = this.numComps;
 
@@ -297,7 +308,7 @@ var PDFImage = (function PDFImageClosure() {
       }
     },
 
-    getComponents: function PDFImage_getComponents(buffer) {
+    getComponents(buffer) {
       var bpc = this.bpc;
 
       // This image doesn't require any extra work.
@@ -374,8 +385,7 @@ var PDFImage = (function PDFImageClosure() {
       return output;
     },
 
-    fillOpacity: function PDFImage_fillOpacity(rgbaBuf, width, height,
-                                               actualHeight, image) {
+    fillOpacity(rgbaBuf, width, height, actualHeight, image) {
       var smask = this.smask;
       var mask = this.mask;
       var alphaBuf, sw, sh, i, ii, j;
@@ -441,7 +451,7 @@ var PDFImage = (function PDFImageClosure() {
       }
     },
 
-    undoPreblend: function PDFImage_undoPreblend(buffer, width, height) {
+    undoPreblend(buffer, width, height) {
       var matte = this.smask && this.smask.matte;
       if (!matte) {
         return;
@@ -472,7 +482,7 @@ var PDFImage = (function PDFImageClosure() {
       }
     },
 
-    createImageData: function PDFImage_createImageData(forceRGBA) {
+    createImageData(forceRGBA = false) {
       var drawWidth = this.drawWidth;
       var drawHeight = this.drawHeight;
       var imgData = { // other fields are filled in below
@@ -581,7 +591,7 @@ var PDFImage = (function PDFImageClosure() {
       return imgData;
     },
 
-    fillGrayBuffer: function PDFImage_fillGrayBuffer(buffer) {
+    fillGrayBuffer(buffer) {
       var numComps = this.numComps;
       if (numComps !== 1) {
         throw new FormatError(
@@ -627,9 +637,7 @@ var PDFImage = (function PDFImageClosure() {
       }
     },
 
-    getImageBytes: function PDFImage_getImageBytes(length,
-                                                   drawWidth, drawHeight,
-                                                   forceRGB) {
+    getImageBytes(length, drawWidth, drawHeight, forceRGB = false) {
       this.image.reset();
       this.image.drawWidth = drawWidth || this.width;
       this.image.drawHeight = drawHeight || this.height;