Revert of Change SkShader;asFragmentProcessor signature to no longer take skpaint\grcolor* (patchset #8 id:140001 of https://codereview.chromium.org/1316513002/ )

Reason for revert:
Primary suspect in failing DEPS rolls:
* https://codereview.chromium.org/1315753006
* https://codereview.chromium.org/1308323006
* https://codereview.chromium.org/1320903004

Primary suspect because the failing win bots did not fail in https://codereview.chromium.org/1315753005

Original issue's description:
> Change SkShader;asFragmentProcessor signature to no longer take skpaint\grcolor*
>
> Committed: https://skia.googlesource.com/skia/+/ecfdc251be71f3d634e76afdd6375bf55fc061aa

TBR=joshualitt@google.com,wangyix@google.com,robertphillips@google.com,bsalomon@google.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Review URL: https://codereview.chromium.org/1313573005

1 files changed, 18 insertions, 11 deletions

diff --git a/include/core/SkShader.h b/include/core/SkShader.h
index 8aaaf52047..47fdc9492f 100644
--- a/include/core/SkShader.h
+++ b/include/core/SkShader.h
@@ -334,20 +334,27 @@ public:
 
 
     /**
-     *  Returns a GrFragmentProcessor that implements the shader for the GPU backend. NULL is
-     *  returned if there is no GPU implementation.
+     *  Returns true if the shader subclass succeeds in creating an effect or if none is required.
+     *  False is returned if it fails or if there is not an implementation of this method in the
+     *  shader subclass.
      *
-     *  The GPU device does not call SkShader::createContext(), instead we pass the view matrix,
-     *  local matrix, and filter quality directly.
+     *  On success an implementation of this method must inspect the SkPaint and set paintColor to
+     *  the color the effect expects as its input color. If the SkShader wishes to emit a solid
+     *  color then it should set paintColor to that color and not create an effect. Note that
+     *  GrColor is always premul. The common patterns are to convert paint's SkColor to GrColor or
+     *  to extract paint's alpha and replicate it to all channels in paintColor. Upon failure
+     *  paintColor should not be modified. It is not recommended to specialize the effect to
+     *  the paint's color as then many GPU shaders may be generated.
      *
-     *  The GrContext may be used by the to create textures that are required by the returned
-     *  processor.
+     *  The GrContext may be used by the effect to create textures. The GPU device does not
+     *  call createContext. Instead we pass the SkPaint here in case the shader needs paint info.
+     *
+     *  A view matrix is always required to create the correct GrFragmentProcessor.  Some shaders
+     *  may also use the optional localMatrix to define a matrix relevant only for sampling.
      */
-    virtual const GrFragmentProcessor* asFragmentProcessor(GrContext*,
-                                                           const SkMatrix& viewMatric,
-                                                           const SkMatrix* localMatrix,
-                                                           SkFilterQuality,
-                                                           GrProcessorDataManager*) const;
+    virtual bool asFragmentProcessor(GrContext*, const SkPaint&, const SkMatrix& viewM,
+                                     const SkMatrix* localMatrix, GrColor*,
+                                     GrProcessorDataManager*, GrFragmentProcessor**) const;
 
     /**
      *  If the shader can represent its "average" luminance in a single color, return true and