add 4f support to colorfiltershader

src/core/SkColorFilterShader.cpp

Index: src/core/SkColorFilterShader.cpp
diff --git a/src/core/SkColorFilterShader.cpp b/src/core/SkColorFilterShader.cpp
index dc90f95762a3398c5f2a964510e75c2803aa4491..81123f6dffc8425da3d6a122bb6b7e72bbd1958e 100644
--- a/src/core/SkColorFilterShader.cpp
+++ b/src/core/SkColorFilterShader.cpp
@@ -43,10 +43,15 @@ uint32_t SkColorFilterShader::FilterShaderContext::getFlags() const {
     uint32_t shaderF = fShaderContext->getFlags();
     uint32_t filterF = filterShader.fFilter->getFlags();
 
-    // if the filter might change alpha, clear the opaque flag in the shader
+    // If the filter does not support a given feature, but sure to clear the corresponding flag
+    // in the shader flags.
+    //
     if (!(filterF & SkColorFilter::kAlphaUnchanged_Flag)) {
         shaderF &= ~SkShader::kOpaqueAlpha_Flag;
     }
+    if (!(filterF & SkColorFilter::kSupports4f_Flag)) {
+        shaderF &= ~SkShader::kSupports4f_Flag;
+    }
     return shaderF;
 }
 
@@ -84,6 +89,14 @@ void SkColorFilterShader::FilterShaderContext::shadeSpan(int x, int y, SkPMColor
     filterShader.fFilter->filterSpan(result, count, result);
 }
 
+void SkColorFilterShader::FilterShaderContext::shadeSpan4f(int x, int y, SkPM4f result[],
+                                                          int count) {
+    const SkColorFilterShader& filterShader = static_cast<const SkColorFilterShader&>(fShader);
+
+    fShaderContext->shadeSpan4f(x, y, result, count);
+    filterShader.fFilter->filterSpan4f(result, count, result);
+}
+
 #if SK_SUPPORT_GPU
 /////////////////////////////////////////////////////////////////////