Oilpan: Added gyp flag to dump points-to graph information from the Blink GC plugin.

Source/config.gyp

Index: Source/config.gyp
diff --git a/Source/config.gyp b/Source/config.gyp
index b9597f43dca29d0ee0cd41bb81b53af80e94c71a..ebebae6556332c8ff4804729cd49fdd2ca5c2279 100644
--- a/Source/config.gyp
+++ b/Source/config.gyp
@@ -37,6 +37,7 @@
     # Requires building locally since GOMA doesn't yet support the plugin.
     'enable_oilpan%': 0,
     'blink_gc_plugin%': 0,
+    'blink_gc_plugin_dump_graph%': 0,
   },
   'targets': [
   {
@@ -105,7 +106,7 @@
         }],
         # Only enable the blink_gc_plugin when using clang and chrome plugins.
         ['blink_gc_plugin==1 and clang==1 and clang_use_chrome_plugins==1', {
-          'cflags': ['<!@(../../../tools/clang/scripts/blink_gc_plugin_flags.sh enable-oilpan=<(enable_oilpan))'],
+          'cflags': ['<!@(../../../tools/clang/scripts/blink_gc_plugin_flags.sh enable-oilpan=<(enable_oilpan) dump-graph=<(blink_gc_plugin_dump_graph))'],
         }],
       ],
     },