Compile V8 with the heap verification feature compiled in

It still has to be enabled via a command line flag

BUG=chromium:449943
R=svenpanne@chromium.org

Review URL: https://codereview.chromium.org/811763006

Cr-Original-Commit-Position: refs/heads/master@{#312185}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 6de75a6db30f690fbf524d3ebc3a7436b5e61cec

common.gypi

@@ -1456,6 +1456,10 @@
     # Compile d8 for the host toolset.
     'v8_toolset_for_d8': 'host',
 
+    # Enable the V8 heap verification code. The verification itself is enabled
+    # via a command line option.
+    'v8_enable_verify_heap%': 1,
+
     # Use brlapi from brltty for braille display support.
     'use_brlapi%': 0,