Add a missing {{streamlen}} in rectangles.in.

README.in points to rectangles.in as an example of how .in files should
be styled. Add the {{streamlen}} to encourage its use.

Change-Id: I58726179913bafe91c9c04b82f5c70573ed478ad
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/59973
Commit-Queue: Lei Zhang <thestig@chromium.org>
Reviewed-by: Henrique Nakashima <hnakashima@chromium.org>
diff --git a/testing/resources/rectangles.in b/testing/resources/rectangles.in
index 49932ff..ee915b7 100644
--- a/testing/resources/rectangles.in
+++ b/testing/resources/rectangles.in
@@ -18,6 +18,7 @@
 >>
 endobj
 {{object 4 0}} <<
+  {{streamlen}}
 >>
 stream
 q
diff --git a/testing/resources/rectangles.pdf b/testing/resources/rectangles.pdf
index 7bad251..bdb6254 100644
--- a/testing/resources/rectangles.pdf
+++ b/testing/resources/rectangles.pdf
@@ -19,6 +19,7 @@
 >>
 endobj
 4 0 obj <<
+  /Length 188
 >>
 stream
 q
@@ -44,7 +45,10 @@
 0000000068 00000 n 
 0000000161 00000 n 
 0000000230 00000 n 
-trailer<< /Root 1 0 R /Size 5 >>
+trailer <<
+  /Root 1 0 R
+  /Size 5
+>>
 startxref
-456
+470
 %%EOF