[Code Coverage] add pdfium_embeddertests to the test suite.

TBR=inferno@chromium.org,tsepez@chromium.org

Bug: 789981
Change-Id: Iaf8f289ca01a78c194a54a5ecdbb9ca3c13a057d
Reviewed-on: https://chromium-review.googlesource.com/1060527
Commit-Queue: Max Moroz <mmoroz@chromium.org>
Reviewed-by: Max Moroz <mmoroz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#558879}

tools/code_coverage/test_suite.txt

@@ -54,6 +54,7 @@ nacl_loader_unittests
 native_theme_unittests
 net_unittests
 pdf_unittests
+pdfium_embeddertests
 pdfium_unittests
 ppapi_unittests
 printing_unittests