Mojo Windows: test_structs.mojom C++ bindings don't compile

See https://codereview.chromium.org/832583002/#msg8

The V10 constant from mojo/public/interfaces/bindings/tests/test_structs.mojom below is the minimum value for an int32.

struct IntegerNumberValues {
  ...
  const int32 V10 = -2147483648;
  ...
}

MSVC can't parse -2147483648, see http://msdn.microsoft.com/en-us/library/4kh09110.aspx

The V10 constant below is the mininum value for an int32.

BUG=445618
R=jimbe@chromium.org

Review URL: https://codereview.chromium.org/830673002