Fix build for x64 arch

media_info_get_size waits unsigned long long not uint64_t
even if it seems to be the same in 32 bits arch.

=> int media_info_get_size(media_info_h media, unsigned long long *size)

log:

[   27s] content/content_instance.cc: In member function 'void ContentItem::init(media_info_h)':
[   27s] content/content_instance.cc:313:38: error: invalid conversion from 'uint64_t* {aka long unsigned int*}' to 'long long unsigned int*' [-fpermissive]
[   27s]    if (media_info_get_size(handle, &ll) == MEDIA_CONTENT_ERROR_NONE)
[   27s]                                       ^

BUG=https://crosswalk-project.org/jira/browse/XWALK-1346

Signed-off-by: Baptiste DURAND <baptiste.durand@open.eurogiciel.org>