Remove SK_SUPPORT_LEGACY_DEEPFLATTENING.

This was needed for pictures before v33, and we're now requiring v35+.

Will follow up with the same for skia/ext/pixel_ref_utils_unittest.cc

BUG=skia:

Committed: https://skia.googlesource.com/skia/+/52c293547b973f7fb5de3c83f5062b07d759ab88

Review URL: https://codereview.chromium.org/769953002
diff --git a/include/effects/SkPerlinNoiseShader.h b/include/effects/SkPerlinNoiseShader.h
index 2937926..fc67484 100644
--- a/include/effects/SkPerlinNoiseShader.h
+++ b/include/effects/SkPerlinNoiseShader.h
@@ -103,9 +103,6 @@
     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkPerlinNoiseShader)
 
 protected:
-#ifdef SK_SUPPORT_LEGACY_DEEPFLATTENING
-    SkPerlinNoiseShader(SkReadBuffer&);
-#endif
     virtual void flatten(SkWriteBuffer&) const SK_OVERRIDE;
     virtual Context* onCreateContext(const ContextRec&, void* storage) const SK_OVERRIDE;
 
@@ -115,16 +112,13 @@
                         const SkISize* tileSize);
     virtual ~SkPerlinNoiseShader();
 
-    // TODO (scroggo): Once all SkShaders are created from a factory, and we have removed the
-    // constructor that creates SkPerlinNoiseShader from an SkReadBuffer, several fields can
-    // be made constant.
-    /*const*/ SkPerlinNoiseShader::Type fType;
-    /*const*/ SkScalar                  fBaseFrequencyX;
-    /*const*/ SkScalar                  fBaseFrequencyY;
-    /*const*/ int                       fNumOctaves;
-    /*const*/ SkScalar                  fSeed;
-    /*const*/ SkISize                   fTileSize;
-    /*const*/ bool                      fStitchTiles;
+    const SkPerlinNoiseShader::Type fType;
+    const SkScalar                  fBaseFrequencyX;
+    const SkScalar                  fBaseFrequencyY;
+    const int                       fNumOctaves;
+    const SkScalar                  fSeed;
+    const SkISize                   fTileSize;
+    const bool                      fStitchTiles;
 
     typedef SkShader INHERITED;
 };