Only allow allow_exhaustive_searches for FC_GRAPHICS_ANIMATION content
Only allow allow_exhaustive_searches for FC_GRAPHICS_ANIMATION content

The allow_exhaustive_searches feature improves the encoding quality
of FC_GRAPHICS_ANIMATION content a lot. For non-FC_GRAPHICS_ANIMATION
content, the quality test result is almost neutral. This patch makes
this feature to be used only for FC_GRAPHICS_ANIMATION content.

The motivation of doing that is to make this feature no longer adaptive,
which will be implemented in the following patch.

Change-Id: Ic911df6dd757402b6480789cc247801e99840369

webmproject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,ShiftMediaProject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx