Hack around broken snapshot generation in the GN build on Android.

The generated snapshot just crashes on the device, but
disabling snapshots allows us to run V8 just fine which
is sufficient for our purposes at this point.

Mojo/Sky are GN-only so we depend on the V8 GN build even if
it's not considered production for Chromium yet.

R=jochen@chromium.org

Review URL: https://codereview.chromium.org/832413005

Cr-Commit-Position: refs/heads/master@{#25982}

BUILD.gn

@@ -17,7 +17,8 @@ v8_enable_verify_heap = false
 v8_interpreted_regexp = false
 v8_object_print = false
 v8_postmortem_support = false
-v8_use_snapshot = true
+# TODO(eseidel): The snapshot generated by the GN Android build crashes.
+v8_use_snapshot = !is_android
 v8_enable_extra_checks = is_debug
 v8_target_arch = cpu_arch
 v8_random_seed = "314159265"