Build render_pdfs on buildbot.

Review URL: https://codereview.appspot.com/7134055

git-svn-id: http://skia.googlecode.com/svn/trunk@7274 2bbb7eff-a529-9590-31e7-b0007b416f81

gyp/tools.gyp

@@ -19,6 +19,7 @@
         'skhello',
         'skimage',
         'render_pictures',
+        'render_pdfs',
         'bench_pictures',
         'pinspect',
         'filter',