Refactor read and write buffers.

Eliminates SkFlattenable{Read,Write}Buffer, promoting SkOrdered{Read,Write}Buffer
a step each in the hierarchy.

What used to be this:

SkFlattenableWriteBuffer -> SkOrderedWriteBuffer
SkFlattenableReadBuffer  -> SkOrderedReadBuffer
SkFlattenableReadBuffer  -> SkValidatingReadBuffer

is now

SkWriteBuffer
SkReadBuffer -> SkValidatingReadBuffer

Benefits:
  - code is simpler, names are less wordy
  - the generic SkFlattenableFooBuffer code in SkPaint was incorrect; removed
  - write buffers are completely devirtualized, important for record speed

This refactoring was mostly mechanical.  You aren't going to find anything
interesting in files with less than 10 lines changed.

BUG=skia:
R=reed@google.com, scroggo@google.com, djsollen@google.com, mtklein@google.com

Author: mtklein@chromium.org

Review URL: https://codereview.chromium.org/134163010

git-svn-id: http://skia.googlecode.com/svn/trunk@13245 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/effects/gradients/SkGradientShader.cpp b/src/effects/gradients/SkGradientShader.cpp
index 6925ad2..1da259a 100644
--- a/src/effects/gradients/SkGradientShader.cpp
+++ b/src/effects/gradients/SkGradientShader.cpp
@@ -143,7 +143,7 @@
     return packed >> 4;
 }
 
-SkGradientShaderBase::SkGradientShaderBase(SkFlattenableReadBuffer& buffer) : INHERITED(buffer) {
+SkGradientShaderBase::SkGradientShaderBase(SkReadBuffer& buffer) : INHERITED(buffer) {
     fCacheAlpha = 256;
 
     fMapper = buffer.readUnitMapper();
@@ -205,7 +205,7 @@
     fColorsAreOpaque = colorAlpha == 0xFF;
 }
 
-void SkGradientShaderBase::flatten(SkFlattenableWriteBuffer& buffer) const {
+void SkGradientShaderBase::flatten(SkWriteBuffer& buffer) const {
     this->INHERITED::flatten(buffer);
     buffer.writeFlattenable(fMapper);
     buffer.writeColorArray(fOrigColors, fColorCount);