TilingPattern: Reverse transform after painting

This transform resulted in an incorrectly positioned object when the
bounding box's upper-left corner did not start at (0,0), because
the translation was not reverted. This patch adds the missing transform.

The test file (tiling-pattern-box.pdf) is based on the PDF from #2825.
All but the first cube (including the PDF data) have been removed.
To trigger the bug that is fixed by this commit, I changed the BBox of
the first pattern from "[ 0 0 596 842]" to "[90 0 596 842]". Without
this patch, the dashed vertical line that intersects the corners at A
and E would disappear.

src/display/pattern_helper.js

@@ -364,6 +364,8 @@ var TilingPattern = (function TilingPatternClosure() {
 
       graphics.executeOperatorList(operatorList);
 
+      this.ctx.transform(1, 0, 0, 1, x0, y0);
+
       // Rescale canvas so that the ctx.createPattern call generates a pattern
       // with the desired size.
       this.ctx.scale(1 / dimx.scale, 1 / dimy.scale);

test/pdfs/.gitignore

@@ -340,4 +340,5 @@
 !issue9972-1.pdf
 !issue9972-2.pdf
 !issue9972-3.pdf
+!tiling-pattern-box.pdf
 !tiling-pattern-large-steps.pdf

test/test_manifest.json

@@ -2996,6 +2996,14 @@
        "link": false,
        "type": "eq"
     },
+    {
+       "id": "tiling-pattern-box",
+       "file": "pdfs/tiling-pattern-box.pdf",
+       "md5": "09100872824fc14012bd8f9bf4dbc632",
+       "rounds": 1,
+       "link": false,
+       "type": "eq"
+    },
     {
        "id": "tiling-pattern-large-steps",
        "file": "pdfs/tiling-pattern-large-steps.pdf",