SkPDF/Bench: add bench for SkPDFSharedStream (deflate)

Also, simplify gyp.

BUG=skia:5009
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1730833003

Review URL: https://codereview.chromium.org/1730833003
diff --git a/gyp/bench.gypi b/gyp/bench.gypi
index bf295cb..69e7086 100644
--- a/gyp/bench.gypi
+++ b/gyp/bench.gypi
@@ -10,12 +10,14 @@
     '../src/core',
     '../src/effects',
     '../src/gpu',
+    '../src/pdf',
     '../src/utils',
   ],
   'sources': [ '<!@(python find.py ../bench "*.cpp")' ],
 
   'dependencies': [
     'etc1.gyp:libetc1',
+    'pdf.gyp:pdf',
     'skia_lib.gyp:skia_lib',
     'tools.gyp:resources',
     'tools.gyp:sk_tool_utils',