Revert "Eliminate unreachable code during optimization."

This reverts commit c6260f974261ee9fb5dc9573669559d728a856e8.

Reason for revert: Nexus 7 is grumpy, fails SkSLDeadReturn_GPU
https://ci.chromium.org/raw/build/logs.chromium.org/skia/539fff50ff093c11/+/annotations


Original change's description:
> Eliminate unreachable code during optimization.
>
> The Adreno 5xx and 6xx previously failed the SkSLStaticSwitchInline
> test; the driver struggled to interpret code with multiple return
> statements in a row. We now detect unreachable statements and eliminate
> them.
>
> Change-Id: I344d632f2488ca65b0635b37bebffe6e4fb607c5
> Bug: skia:12012
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/410256
> Auto-Submit: John Stiles <johnstiles@google.com>
> Commit-Queue: Brian Osman <brianosman@google.com>
> Reviewed-by: Brian Osman <brianosman@google.com>

TBR=brianosman@google.com,ethannicholas@google.com,johnstiles@google.com

Change-Id: Ia3db1f1b28417e479e2d71a4a6ed94a007e47cf9
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:12012
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/410780
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
17 files changed