Add a pixel test for filling 2-point paths.

Add a pixel test for filling paths with only 2 points, which should all
be rendered as thin lines even if they don't form closed areas.

The expected result represents the current rendering behavior of PDFium,
which should be updated once the bug is fixed.

Bug: pdfium:1639
Change-Id: If7424f82d5c3ba787a710999970aed5536ea9bed
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/78210
Commit-Queue: Hui Yingst <nigi@chromium.org>
Reviewed-by: Daniel Hosseinian <dhoss@chromium.org>

testing/resources/pixel/bug_1639_1.in

diff --git a/testing/resources/pixel/bug_1639_1.in b/testing/resources/pixel/bug_1639_1.in
new file mode 100644
index 0000000..f283af7
--- /dev/null
+++ b/testing/resources/pixel/bug_1639_1.in
@@ -0,0 +1,50 @@
+{{header}}
+{{object 1 0}} <<
+  /Type /Catalog
+  /Pages 2 0 R
+>>
+endobj
+{{object 2 0}} <<
+  /Type /Pages
+  /Count 1
+  /Kids [3 0 R]
+>>
+endobj
+{{object 3 0}} <<
+  /Type /Page
+  /Parent 2 0 R
+  /Contents 4 0 R
+  /MediaBox [0 0 200 200]
+  /Resources <<
+    /ExtGState <<
+      /GS1 <<
+        /ca 1.0
+      >>
+    >>
+  >>
+>>
+endobj
+{{object 4 0}} <<
+  {{streamlen}}
+>>
+stream
+q
+/GS1 gs
+0 0 1 rg
+% A horizontal path.
+20 180 m
+180 180 l
+% A vertical path.
+50 160 m
+50 100 l
+% A diagonal path.
+20 50 m
+180 100 l
+f
+Q
+endstream
+endobj
+{{xref}}
+{{trailer}}
+{{startxref}}
+%%EOF

testing/resources/pixel/bug_1639_1_expected.pdf.0.png

diff --git a/testing/resources/pixel/bug_1639_1_expected.pdf.0.png b/testing/resources/pixel/bug_1639_1_expected.pdf.0.png
new file mode 100644
index 0000000..f97e340
--- /dev/null
+++ b/testing/resources/pixel/bug_1639_1_expected.pdf.0.png
Binary files differ