Convert PDFFunction to a standard class with static methods

For e.g. `gulp mozcentral`, the *built* `pdf.worker.js` file decreases from `1 837 608` to `1 834 907` bytes with this patch-series.
The improvement comes first of all from less overall indentation in `PDFFunction`, and secondly from the removal of (now) unnecessary indirection in the code.

src/core/function.js

@@ -131,9 +131,8 @@ function toNumberArray(arr) {
   return arr;
 }
 
-const PDFFunction = (function PDFFunctionClosure() {
-  return {
-    getSampleArray(size, outputSize, bps, stream) {
+class PDFFunction {
+  static getSampleArray(size, outputSize, bps, stream) {
     let i, ii;
     let length = 1;
     for (i = 0, ii = size.length; i < ii; i++) {
@@ -160,9 +159,9 @@ const PDFFunction = (function PDFFunctionClosure() {
       codeBuf &= (1 << codeSize) - 1;
     }
     return array;
-    },
+  }
 
-    parse({ xref, isEvalSupported, fn }) {
+  static parse({ xref, isEvalSupported, fn }) {
     const dict = fn.dict || fn;
     const typeNum = dict.get("FunctionType");
 
@@ -179,9 +178,9 @@ const PDFFunction = (function PDFFunctionClosure() {
         return this.constructPostScript({ xref, isEvalSupported, fn, dict });
     }
     throw new FormatError("Unknown type of function");
-    },
+  }
 
-    parseArray({ xref, isEvalSupported, fnObj }) {
+  static parseArray({ xref, isEvalSupported, fnObj }) {
     if (!Array.isArray(fnObj)) {
       // not an array -- parsing as regular function
       return this.parse({ xref, isEvalSupported, fn: fnObj });
@@ -198,9 +197,9 @@ const PDFFunction = (function PDFFunctionClosure() {
         fnArray[i](src, srcOffset, dest, destOffset + i);
       }
     };
-    },
+  }
 
-    constructSampled({ xref, isEvalSupported, fn, dict }) {
+  static constructSampled({ xref, isEvalSupported, fn, dict }) {
     function toMultiArray(arr) {
       const inputLength = arr.length;
       const out = [];
@@ -328,15 +327,12 @@ const PDFFunction = (function PDFFunctionClosure() {
         rj = interpolate(rj, 0, 1, decode[j][0], decode[j][1]);
 
         // y_j = min(max(r_j, range_2j), range_2j+1)
-          dest[destOffset + j] = Math.min(
-            Math.max(rj, range[j][0]),
-            range[j][1]
-          );
+        dest[destOffset + j] = Math.min(Math.max(rj, range[j][0]), range[j][1]);
       }
     };
-    },
+  }
 
-    constructInterpolated({ xref, isEvalSupported, dict }) {
+  static constructInterpolated({ xref, isEvalSupported, dict }) {
     const c0 = toNumberArray(dict.getArray("C0")) || [0];
     const c1 = toNumberArray(dict.getArray("C1")) || [1];
     const n = dict.get("N");
@@ -347,21 +343,16 @@ const PDFFunction = (function PDFFunctionClosure() {
     }
     const length = diff.length;
 
-      return function constructInterpolatedFn(
-        src,
-        srcOffset,
-        dest,
-        destOffset
-      ) {
+    return function constructInterpolatedFn(src, srcOffset, dest, destOffset) {
       const x = n === 1 ? src[srcOffset] : src[srcOffset] ** n;
 
       for (let j = 0; j < length; ++j) {
         dest[destOffset + j] = c0[j] + x * diff[j];
       }
     };
-    },
+  }
 
-    constructStiched({ xref, isEvalSupported, dict }) {
+  static constructStiched({ xref, isEvalSupported, dict }) {
     const domain = toNumberArray(dict.getArray("Domain"));
 
     if (!domain) {
@@ -429,9 +420,9 @@ const PDFFunction = (function PDFFunctionClosure() {
       // call the appropriate function
       fns[i](tmpBuf, 0, dest, destOffset);
     };
-    },
+  }
 
-    constructPostScript({ xref, isEvalSupported, fn, dict }) {
+  static constructPostScript({ xref, isEvalSupported, fn, dict }) {
     const domain = toNumberArray(dict.getArray("Domain"));
     const range = toNumberArray(dict.getArray("Range"));
 
@@ -454,13 +445,7 @@ const PDFFunction = (function PDFFunctionClosure() {
         // subtraction, Math.max, and also contains 'var' and 'return'
         // statements. See the generation in the PostScriptCompiler below.
         // eslint-disable-next-line no-new-func
-          return new Function(
-            "src",
-            "srcOffset",
-            "dest",
-            "destOffset",
-            compiled
-          );
+        return new Function("src", "srcOffset", "dest", "destOffset", compiled);
       }
     }
     info("Unable to compile PS function");
@@ -515,9 +500,8 @@ const PDFFunction = (function PDFFunctionClosure() {
       }
       dest.set(output, destOffset);
     };
-    },
-  };
-})();
+  }
+}
 
 function isPDFFunction(v) {
   let fnDict;