Revert of add ImageShader, sharing code with its Bitmap cousin (patchset #10 id:18000...

Revert of add ImageShader, sharing code with its Bitmap cousin (patchset #10 id:180001 of https://codereview.chromium.org/1342113002/ )

Reason for revert:
Failing ImageNewShaderTest on both Android (Tegra3 GPU) and iOS bots.

e.g.

/Users/chrome-bot/buildbot/skiabot-ipad4-000/build/slave/workdir/build/skia/tests/
	ImageNewShaderTest.cpp:24	0 == memcmp(bm1.getPixels(), bm2.getPixels(), bm1.getSize())
	ImageNewShaderTest.cpp:95	0xFFFF0000 == bmt.getColor(0, y)
	ImageNewShaderTest.cpp:98	0xFFDEDEDE == bmt.getColor(x, y)
	ImageNewShaderTest.cpp:98	0xFFDEDEDE == bmt.getColor(x, y)
	ImageNewShaderTest.cpp:98	0xFFDEDEDE == bmt.getColor(x, y)
	ImageNewShaderTest.cpp:98	0xFFDEDEDE == bmt.getColor(x, y)
	ImageNewShaderTest.cpp:95	0xFFFF0000 == bmt.getColor(0, y)
...

Original issue's description:
> add ImageShader, sharing code with its Bitmap cousin
>
> This is done by having abstracted the BitmapShaderContext to take a BitmapProvider, instead of just a bitmap. This allows us to share all of that code between SkBitmap and SkImage, since both are valid providers.
>
> It also means that we can simplify SkImage_Base to not need a virtual for onNewShader, since ALL images can uniformly be turned into a shader now.
>
> BUG=skia:
>
> Committed: https://skia.googlesource.com/skia/+/0b93e3149d2cb30860c51f9f3204ae811d9a97ca

TBR=fmalita@chromium.org,bsalomon@google.com,robertphillips@google.com,reed@google.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=skia:

Review URL: https://codereview.chromium.org/1355863002