Revert of Make GrScratchKey memory buffer correct size on copy (patchset #1 id:1...

Revert of Make GrScratchKey memory buffer correct size on copy (patchset #1 id:1 of https://codereview.chromium.org/860333002/)

Reason for revert:
Our Valgrind bot just spewed out a weird error.  I don't know if it's related, but it looks at least like one of the stacks was in the right area, so I'm going to revert this precautionarily.  Sorry if this is a false positive.

http://build.chromium.org/p/client.skia/builders/Test-Ubuntu12-ShuttleA-GTX550Ti-x86_64-Release-Valgrind/builds/266/steps/dm/logs/stdio

Original issue's description:
> Make GrScratchKey memory buffer correct size on copy
>
> Scratch key memory buffer of a copy of a key was too big. The (new) copy
> was N times uint32_t bytes instead of N bytes.
>
> Adds few tests to resource cache. These tests would not catch the too
> big buffer. This is just a precaution for too small buffers. The main
> idea of the test change is that the scratch key should contain some
> information, so that lookup with a scratch key can also return no
> match. Otherwise testing of scratch lookup result is not indicative of
> correct code (eg. no-information scratch key will always match).
>
> Committed: https://skia.googlesource.com/skia/+/711ef4831363fb8cbdf061dc2c36c65b13c0ccf2

TBR=bsalomon@google.com,kkinnunen@nvidia.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Review URL: https://codereview.chromium.org/864833003