Simplify flattening to just write enough to call the factory

src/core/SkComposeShader.cpp

Index: src/core/SkComposeShader.cpp
diff --git a/src/core/SkComposeShader.cpp b/src/core/SkComposeShader.cpp
index f7de73b205d45d652c2a2c9cfc0f560f2ba7f38b..3c5b55aae663e948e0c740d4dbcde3b9948d790a 100644
--- a/src/core/SkComposeShader.cpp
+++ b/src/core/SkComposeShader.cpp
@@ -26,8 +26,8 @@ SkComposeShader::SkComposeShader(SkShader* sA, SkShader* sB, SkXfermode* mode) {
     SkSafeRef(mode);
 }
 
-SkComposeShader::SkComposeShader(SkReadBuffer& buffer) :
-    INHERITED(buffer) {
+#ifdef SK_SUPPORT_LEGACY_DEEPFLATTENING
+SkComposeShader::SkComposeShader(SkReadBuffer& buffer) : INHERITED(buffer) {
     fShaderA = buffer.readShader();
     if (NULL == fShaderA) {
         fShaderA = SkNEW_ARGS(SkColorShader, ((SkColor)0));
@@ -38,6 +38,7 @@ SkComposeShader::SkComposeShader(SkReadBuffer& buffer) :
     }
     fMode = buffer.readXfermode();
 }
+#endif
 
 SkComposeShader::~SkComposeShader() {
     SkSafeUnref(fMode);
@@ -66,8 +67,17 @@ private:
 };
 #define SkAutoAlphaRestore(...) SK_REQUIRE_LOCAL_VAR(SkAutoAlphaRestore)
 
+SkFlattenable* SkComposeShader::CreateProc(SkReadBuffer& buffer) {
+    SkAutoTUnref<SkShader> shaderA(buffer.readShader());
+    SkAutoTUnref<SkShader> shaderB(buffer.readShader());
+    SkAutoTUnref<SkXfermode> mode(buffer.readXfermode());
+    if (!shaderA.get() || !shaderB.get()) {
+        return NULL;
+    }
+    return SkNEW_ARGS(SkComposeShader, (shaderA, shaderB, mode));
+}
+
 void SkComposeShader::flatten(SkWriteBuffer& buffer) const {
-    this->INHERITED::flatten(buffer);
     buffer.writeFlattenable(fShaderA);
     buffer.writeFlattenable(fShaderB);
     buffer.writeFlattenable(fMode);