Add tests for GetNamedDests() API.

testing/resources/named_dests.pdf

Index: testing/resources/named_dests.pdf
diff --git a/testing/resources/named_dests.pdf b/testing/resources/named_dests.pdf
new file mode 100644
index 0000000000000000000000000000000000000000..1f650e7865e1a62fa247fee5bf3648a5ef85189f
--- /dev/null
+++ b/testing/resources/named_dests.pdf
@@ -0,0 +1,87 @@
+%PDF-1.7
+% ò¤ô
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+  /Type /Pages
+  /Count 1
+  /Kids [3 0 R]
+>>
+endobj
+2 0 obj <<
+  /Type /Catalog
+  /Pages 1 0 R
+  /Names <<
+    /Dests 10 0 R
+  >>
+  /Dests 14 0 R
+>>
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+endobj
+% Root of Dests NameTree
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+endobj
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+    (Next) <</D [4 /Fit]>>
+  ]
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+endobj
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+  /Names [
+    (WrongKey)  <</Fail [10 /FitH]>>
+    (WrongType) /NameNotAllowedHere
+  ]
+>>
+endobj
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+  /FirstAlternate [10 /XYZ 200 400 800]
+  /LastAlternate  <</D [14 /XYZ 0 0 -200]>>
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