Add fuzzer for cmap parsing

testing/libfuzzer/BUILD.gn

Index: testing/libfuzzer/BUILD.gn
diff --git a/testing/libfuzzer/BUILD.gn b/testing/libfuzzer/BUILD.gn
index a872901e77875d46ee7f9d2b2287eb4a50385659..7049add6c578595f737d91387f5e88dd2f8f6eb8 100644
--- a/testing/libfuzzer/BUILD.gn
+++ b/testing/libfuzzer/BUILD.gn
@@ -154,6 +154,21 @@ if (pdf_enable_xfa) {
   }
 }
 
+source_set("pdf_cmap_fuzzer") {
+  testonly = true
+  sources = [
+    "pdf_cmap_fuzzer.cc",
+  ]
+  deps = [
+    "//third_party/pdfium:pdfium",
+  ]
+  configs -= [ "//build/config/compiler:chromium_code" ]
+  configs += [
+    "//build/config/compiler:no_chromium_code",
+    ":libfuzzer_config",
+  ]
+}
+
 source_set("pdf_codec_fax_fuzzer") {
   testonly = true
   sources = [