Memory improvements to render_pdfs; better DM pool size defaults

gyp/common_conditions.gypi

 # conditions used in both common.gypi and skia.gyp in chromium
 #
 {
   'defines': [
     'SK_ALLOW_STATIC_GLOBAL_INITIALIZERS=<(skia_static_initializers)',
     'SK_SUPPORT_GPU=<(skia_gpu)',
     'SK_SUPPORT_OPENCL=<(skia_opencl)',
     'SK_FORCE_DISTANCEFIELD_FONTS=<(skia_force_distancefield_fonts)',
+    'SK_DEFAULT_RESOURCE_CACHE_MB_LIMIT=<(skia_resource_cache_mb_limit)',
   ],
   'conditions' : [
     ['skia_pic', {
      'cflags': [
        '-fPIC',
      ],
      'conditions' : [
       # FIXME: The reason we don't do this on Android is due to the way
       # we build the executables/skia_launcher on Android. See
       # https://codereview.chromium.org/406613003/diff/1/gyp/common_conditions.gypi#newcode455
@@ skipping 660 matching lines @@
     [ 'skia_is_bot', {
       'defines': [ 'SK_CRASH_HANDLER' ],
     }],
 
   ], # end 'conditions'
   # The Xcode SYMROOT must be at the root. See build/common.gypi in chromium for more details
   'xcode_settings': {
     'SYMROOT': '<(DEPTH)/xcodebuild',
   },
 }