Simplify flattening to just write enough to call the factory

gm/imagefiltersbase.cpp

Index: gm/imagefiltersbase.cpp
diff --git a/gm/imagefiltersbase.cpp b/gm/imagefiltersbase.cpp
index bbcb7ce2b567a6dc7e370c8de77d4c55da6963ca..f0637118e0c5e5bda28d978c29a926ce6f7b2bf4 100644
--- a/gm/imagefiltersbase.cpp
+++ b/gm/imagefiltersbase.cpp
@@ -30,13 +30,19 @@ protected:
         return false;
     }
 
-    FailImageFilter(SkReadBuffer& buffer)
-      : INHERITED(0, buffer) {}
+#ifdef SK_SUPPORT_LEGACY_DEEPFLATTENING
+    FailImageFilter(SkReadBuffer& buffer) : INHERITED(0, buffer) {}
+#endif
 
 private:
     typedef SkImageFilter INHERITED;
 };
 
+SkFlattenable* FailImageFilter::CreateProc(SkReadBuffer& buffer) {
+    SK_IMAGEFILTER_UNFLATTEN_COMMON(0);
+    return FailImageFilter::Create();
+}
+
 // register the filter with the flattenable registry
 static SkFlattenable::Registrar gFailImageFilterReg("FailImageFilter",
                                                     FailImageFilter::CreateProc,
@@ -58,13 +64,19 @@ protected:
         return true;
     }
 
-    IdentityImageFilter(SkReadBuffer& buffer)
-      : INHERITED(1, buffer) {}
+#ifdef SK_SUPPORT_LEGACY_DEEPFLATTENING
+    IdentityImageFilter(SkReadBuffer& buffer) : INHERITED(1, buffer) {}
+#endif
 
 private:
     typedef SkImageFilter INHERITED;
 };
 
+SkFlattenable* IdentityImageFilter::CreateProc(SkReadBuffer& buffer) {
+    SK_IMAGEFILTER_UNFLATTEN_COMMON(1);
+    return IdentityImageFilter::Create(common.inputAt(0));
+}
+
 // register the filter with the flattenable registry
 static SkFlattenable::Registrar gIdentityImageFilterReg("IdentityImageFilter",
                                                         IdentityImageFilter::CreateProc,