Revert of Multiply in 64 bits to avoid overflow

Revert of Multiply in 64 bits to avoid overflow (patchset #1 id:1 of https://codereview.webrtc.org/2729573002/ )

Reason for revert:
Looks like this caused isac_fix_test to start failing:
https://build.chromium.org/p/client.webrtc.perf/builders/Linux%20Trusty?numbuilds=200
https://build.chromium.org/p/client.webrtc.perf/builders/Linux%20Trusty/builds/1501

Original issue's description:
> Multiply in 64 bits to avoid overflow
> 
> A fuzzer run caused the operands of this multiplication to be 512 and
> 5000000, resulting in a product about 20% too large for int32_t. So
> change this from a 16x32->32 to a 16x32->64 multiplication. Since we
> right shift by 2 at the end, the end result will still fit in int32_t.
> 
> I also had to fix a few follow-on add/sub overflows found by the same
> fuzzer input once the multiplication was fixed. I chose to saturate
> these, since it wasn't just an intermediate value that overflowed.
> 
> BUG=chromium:693868
> 
> Review-Url: https://codereview.webrtc.org/2729573002
> Cr-Commit-Position: refs/heads/master@{#17003}
> Committed: https://chromium.googlesource.com/external/webrtc/+/3a2c803dc341a2bc266effb07df9863c14a7aeaa

TBR=henrik.lundin@webrtc.org,kwiberg@webrtc.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=chromium:693868

[tommi, 2017-03-11 16:00:50]

The CQ bit was checked by tommi@webrtc.org

[tommi, 2017-03-11 16:00:50]

Created Revert of Multiply in 64 bits to avoid overflow

[commit-bot: I haz the power, 2017-03-11 16:00:56]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.webrtc.org/...

[tommi, 2017-03-11 16:01:42]

The CQ bit was unchecked by tommi@webrtc.org

[tommi, 2017-03-11 16:02:07]

On 2017/03/11 16:00:56, commit-bot: I haz the power wrote:
> CQ is trying da patch. Follow status at
>  
>
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.webrtc.org/...

Not landing the revert since the chromium issue the CL fixed, has been verified.