Revert "SkShaderBase"

This reverts commit 58a756435ca3700d9766a4580bb0771a9774f603.

Reason for revert: g3, Android borkage.

Original change's description:
> SkShaderBase
> 
> Introduce a private base class (SkShaderBase), to hide
> implementation details from the public interface (SkShader).
> 
> Change-Id: If3ec26ca6abc9da20e3f139c11fdc023bdd85176
> Reviewed-on: https://skia-review.googlesource.com/17241
> Commit-Queue: Florin Malita <fmalita@chromium.org>
> Reviewed-by: Mike Reed <reed@google.com>
> 

TBR=mtklein@google.com,fmalita@chromium.org,reed@google.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Change-Id: I32b012ee466dd006c074593f211f43ed602f1078
Reviewed-on: https://skia-review.googlesource.com/17845
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Florin Malita <fmalita@chromium.org>
diff --git a/src/effects/gradients/SkLinearGradient.cpp b/src/effects/gradients/SkLinearGradient.cpp
index 17c4fd3..bd46452 100644
--- a/src/effects/gradients/SkLinearGradient.cpp
+++ b/src/effects/gradients/SkLinearGradient.cpp
@@ -39,11 +39,11 @@
     return matrix;
 }
 
-static bool use_4f_context(const SkShaderBase::ContextRec& rec, uint32_t flags) {
+static bool use_4f_context(const SkShader::ContextRec& rec, uint32_t flags) {
 #ifdef FORCE_4F_CONTEXT
     return true;
 #else
-    return rec.fPreferredDstType == SkShaderBase::ContextRec::kPM4f_DstType
+    return rec.fPreferredDstType == SkShader::ContextRec::kPM4f_DstType
         || SkToBool(flags & SkLinearGradient::kForce4fContext_PrivateFlag);
 #endif
 }
@@ -75,7 +75,7 @@
     buffer.writePoint(fEnd);
 }
 
-SkShaderBase::Context* SkLinearGradient::onMakeContext(
+SkShader::Context* SkLinearGradient::onMakeContext(
     const ContextRec& rec, SkArenaAlloc* alloc) const
 {
     return use_4f_context(rec, fGradFlags)
@@ -436,7 +436,7 @@
         SkGradientShader::MakeLinear(points, params.fColors, params.fStops,
                                      params.fColorCount, params.fTileMode);
     GrTest::TestAsFPArgs asFPArgs(d);
-    sk_sp<GrFragmentProcessor> fp = as_SB(shader)->asFragmentProcessor(asFPArgs.args());
+    sk_sp<GrFragmentProcessor> fp = shader->asFragmentProcessor(asFPArgs.args());
     GrAlwaysAssert(fp);
     return fp;
 }