Refactor read and write buffers.

src/effects/gradients/SkSweepGradient.cpp

Index: src/effects/gradients/SkSweepGradient.cpp
diff --git a/src/effects/gradients/SkSweepGradient.cpp b/src/effects/gradients/SkSweepGradient.cpp
index d60d8b6050d8971e624f14f943660a6502403026..494569df5dc23362710933827253144121e19dc4 100644
--- a/src/effects/gradients/SkSweepGradient.cpp
+++ b/src/effects/gradients/SkSweepGradient.cpp
@@ -42,12 +42,12 @@ SkShader::GradientType SkSweepGradient::asAGradient(GradientInfo* info) const {
     return kSweep_GradientType;
 }
 
-SkSweepGradient::SkSweepGradient(SkFlattenableReadBuffer& buffer)
+SkSweepGradient::SkSweepGradient(SkReadBuffer& buffer)
     : INHERITED(buffer),
       fCenter(buffer.readPoint()) {
 }
 
-void SkSweepGradient::flatten(SkFlattenableWriteBuffer& buffer) const {
+void SkSweepGradient::flatten(SkWriteBuffer& buffer) const {
     this->INHERITED::flatten(buffer);
     buffer.writePoint(fCenter);
 }