remove native support for the ability to disable runtime options that REQUIRE the SSE2 instruction set. Users of older hardware, like AMD Athlon XPs for example, need this feature.
A patch for v35/v36 will revert issue #187423002 and allow you to compile with the -Ddisable_sse2=1 switch again.
Here is an Arch PKGBUILD that mirrors that of the official [extra]/chromium I maintain that has this patch enabled.
For v38 code for support non-sse2 x86 machines was removed and more intrusive patches are required. Also build on x86 was broken completely due to SSE4.1 intrinsics which can't be compiled on x86 at all, so a separate patch removes SSE4* instructions on x86.
ATM SSE4 patch is working and SSE2 one is in the process (it should be applied on top of SSE2 one).