Simplify flattening to just write enough to call the factory/public-constructor for the class. We want to *not* rely on private constructors, and not rely on calling through the inheritance hierarchy for either flattening or unflattening(CreateProc).

Refactoring pattern:

1. guard the existing constructor(readbuffer) with the legacy build-flag
2. If you are a instancable subclass, implement CreateProc(readbuffer) to create a new instances from the buffer params (or return NULL).

If you're a shader subclass
1. You must read/write the local matrix if your class accepts that in its factory/constructor, else ignore it.

R=robertphillips@google.com, mtklein@google.com, senorblanco@google.com, senorblanco@chromium.org, sugoi@chromium.org

Author: reed@google.com

Review URL: https://codereview.chromium.org/395603002
diff --git a/src/effects/Sk2DPathEffect.cpp b/src/effects/Sk2DPathEffect.cpp
index 252866c..cef2266 100644
--- a/src/effects/Sk2DPathEffect.cpp
+++ b/src/effects/Sk2DPathEffect.cpp
@@ -73,10 +73,12 @@
     buffer.writeMatrix(fMatrix);
 }
 
+#ifdef SK_SUPPORT_LEGACY_DEEPFLATTENING
 Sk2DPathEffect::Sk2DPathEffect(SkReadBuffer& buffer) {
     buffer.readMatrix(&fMatrix);
     fMatrixIsInvertible = fMatrix.invert(&fInverse);
 }
+#endif
 
 ///////////////////////////////////////////////////////////////////////////////
 
@@ -102,12 +104,21 @@
     }
 }
 
+#ifdef SK_SUPPORT_LEGACY_DEEPFLATTENING
 SkLine2DPathEffect::SkLine2DPathEffect(SkReadBuffer& buffer) : INHERITED(buffer) {
     fWidth = buffer.readScalar();
 }
+#endif
+
+SkFlattenable* SkLine2DPathEffect::CreateProc(SkReadBuffer& buffer) {
+    SkMatrix matrix;
+    buffer.readMatrix(&matrix);
+    SkScalar width = buffer.readScalar();
+    return SkLine2DPathEffect::Create(width, matrix);
+}
 
 void SkLine2DPathEffect::flatten(SkWriteBuffer &buffer) const {
-    this->INHERITED::flatten(buffer);
+    buffer.writeMatrix(this->getMatrix());
     buffer.writeScalar(fWidth);
 }
 
@@ -117,13 +128,22 @@
     : INHERITED(m), fPath(p) {
 }
 
-SkPath2DPathEffect::SkPath2DPathEffect(SkReadBuffer& buffer)
-        : INHERITED(buffer) {
+#ifdef SK_SUPPORT_LEGACY_DEEPFLATTENING
+SkPath2DPathEffect::SkPath2DPathEffect(SkReadBuffer& buffer) : INHERITED(buffer) {
     buffer.readPath(&fPath);
 }
+#endif
+
+SkFlattenable* SkPath2DPathEffect::CreateProc(SkReadBuffer& buffer) {
+    SkMatrix matrix;
+    buffer.readMatrix(&matrix);
+    SkPath path;
+    buffer.readPath(&path);
+    return SkPath2DPathEffect::Create(matrix, path);
+}
 
 void SkPath2DPathEffect::flatten(SkWriteBuffer& buffer) const {
-    this->INHERITED::flatten(buffer);
+    buffer.writeMatrix(this->getMatrix());
     buffer.writePath(fPath);
 }