Remove stale gradient color space assert

SkGradientShaderBase asserts gammaIsLinear() -- but we don't enforce
this in factories.

Based on comments, this may be a stale restriction.  Can we drop it?

Bug: chromium:798208
Change-Id: Id9639cb2bb87f112b26c05372f2a3181c139e5ec
Reviewed-on: https://skia-review.googlesource.com/123860
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Florin Malita <fmalita@chromium.org>
diff --git a/src/shaders/gradients/SkGradientShader.cpp b/src/shaders/gradients/SkGradientShader.cpp
index cb138e0..60b9e34 100644
--- a/src/shaders/gradients/SkGradientShader.cpp
+++ b/src/shaders/gradients/SkGradientShader.cpp
@@ -118,6 +118,7 @@
 SkGradientShaderBase::SkGradientShaderBase(const Descriptor& desc, const SkMatrix& ptsToUnit)
     : INHERITED(desc.fLocalMatrix)
     , fPtsToUnit(ptsToUnit)
+    , fColorSpace(desc.fColorSpace ? desc.fColorSpace : SkColorSpace::MakeSRGBLinear())
     , fColorsAreOpaque(true)
 {
     fPtsToUnit.getType();  // Precache so reads are threadsafe.
@@ -168,16 +169,6 @@
         *origColors = desc.fColors[desc.fCount - 1];
     }
 
-    if (!desc.fColorSpace) {
-        // This happens if we were constructed from SkColors, so our colors are really sRGB
-        fColorSpace = SkColorSpace::MakeSRGBLinear();
-    } else {
-        // The color space refers to the float colors, so it must be linear gamma
-        // TODO: GPU code no longer requires this (see GrGradientEffect). Remove this restriction?
-        SkASSERT(desc.fColorSpace->gammaIsLinear());
-        fColorSpace = desc.fColorSpace;
-    }
-
     if (desc.fPos) {
         SkScalar prev = 0;
         SkScalar* origPosPtr = fOrigPos;