Revert of Makes GrGLProgramDesc's key store the lengths as well as offsets of the effect keys. (https://codereview.chromium.org/379113004/)

Reason for revert:
Most likely candidate for Valgrind failures:

[21:10:08.755668] ==3036== Use of uninitialised value of size 8
[21:10:08.755753] ==3036==    at 0x734AB2: GrGpuGL::ProgramCache::getProgram(GrGLProgramDesc const&, GrEffectStage const**, GrEffectStage const**) (GrGpuGL_program.cpp:107)
[21:10:08.755788] ==3036==    by 0x734ED2: GrGpuGL::flushGraphicsState(GrGpu::DrawType, GrDeviceCoordTexture const*) (GrGpuGL_program.cpp:253)
[21:10:08.755811] ==3036==    by 0x6E81C2: GrGpu::setupClipAndFlushState(GrGpu::DrawType, GrDeviceCoordTexture const*, GrDrawState::AutoRestoreEffects*, SkRect const*) (GrGpu.cpp:350)
[21:10:08.755837] ==3036==    by 0x6E9BE8: GrGpu::onDraw(GrDrawTarget::DrawInfo const&) (GrGpu.cpp:390)
[21:10:08.755858] ==3036==    by 0x6EEECE: GrInOrderDrawBuffer::flush() (GrDrawTarget.h:506)
[21:10:08.755879] ==3036==    by 0x6D0EB4: GrContext::flush(int) (GrContext.cpp:1327)
[21:10:08.755900] ==3036==    by 0x6D3F8F: GrContext::writeTexturePixels(GrTexture*, int, int, int, int, GrPixelConfig, void const*, unsigned long, unsigned int) (GrContext.cpp:1349)
[21:10:08.755922] ==3036==    by 0x6D39D7: GrContext::writeRenderTargetPixels(GrRenderTarget*, int, int, int, int, GrPixelConfig, void const*, unsigned long, unsigned int) (GrContext.cpp:1632)
[21:10:08.755949] ==3036==    by 0x6FFDF3: GrRenderTarget::writePixels(int, int, int, int, GrPixelConfig, void const*, unsigned long, unsigned int) (GrRenderTarget.cpp:45)
[21:10:08.755978] ==3036==    by 0x735563: SkGpuDevice::onWritePixels(SkImageInfo const&, void const*, unsigned long, int, int) (SkGpuDevice.cpp:280)
[21:10:08.756003] ==3036==    by 0x57A048: SkBaseDevice::writePixels(SkImageInfo const&, void const*, unsigned long, int, int) (SkDevice.cpp:106)
[21:10:08.756025] ==3036==    by 0x56D0AE: SkCanvas::writePixels(SkImageInfo const&, void const*, unsigned long, int, int) (SkCanvas.cpp:700)
[21:10:08.756050] ==3036==    by 0x56D156: SkCanvas::writePixels(SkBitmap const&, int, int) (SkCanvas.cpp:652)
[21:10:08.756077] ==3036==    by 0x5109B6: test_WritePixels(skiatest::Reporter*, GrContextFactory*) (WritePixelsTest.cpp:464)
[21:10:08.756099] ==3036==    by 0x51114C: skiatest::WritePixelsClass::onRun(skiatest::Reporter*) (WritePixelsTest.cpp:361)
[21:10:08.756122] ==3036==    by 0x406BE8: skiatest::Test::run() (Test.cpp:107)
[21:10:08.756145] ==3036==    by 0x4064C2: SkTestRunnable::run() (skia_test.cpp:109)
[21:10:08.756167] ==3036==    by 0x405D1A: tool_main(int, char**) (skia_test.cpp:221)
[21:10:08.756189] ==3036==    by 0x405F75: main (skia_test.cpp:239)
[21:10:08.756211] ==3036==  Uninitialised value was created by a stack allocation
[21:10:08.756233] ==3036==    at 0x734CC8: GrGpuGL::flushGraphicsState(GrGpu::DrawType, GrDeviceCoordTexture const*) (GrGpuGL_program.cpp:213)

Original issue's description:
> Makes GrGLProgramDesc's key store the lengths as well as offsets of the effect keys.
>
> Makes it possible to use GrBackendEffectFactories other than GrTBEF by moving meta-key generation out of GrTBEF.
>
> Cleans up docs around GrBackendEffectFactory.
>
> Committed: https://skia.googlesource.com/skia/+/c0ea398aff8254e31152cbb94c9ab6150428e252

R=robertphillips@google.com, jvanverth@google.com, bsalomon@google.com
TBR=bsalomon@google.com, jvanverth@google.com, robertphillips@google.com
NOTREECHECKS=true
NOTRY=true

Author: mtklein@google.com

Review URL: https://codereview.chromium.org/394213002
7 files changed