Hide SkCanvas::{set,get}DrawFilter

Except for Android, which still makes use of it.

BUG=skia:3587
R=reed@google.com,djsollen@google.com
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1618843002

Review URL: https://codereview.chromium.org/1618843002
diff --git a/src/core/SkCanvas.cpp b/src/core/SkCanvas.cpp
index cd7c6f8..d2d7c59 100644
--- a/src/core/SkCanvas.cpp
+++ b/src/core/SkCanvas.cpp
@@ -444,7 +444,11 @@
                    bool skipLayerForImageFilter = false,
                    const SkRect* rawBounds = nullptr) : fOrigPaint(paint) {
         fCanvas = canvas;
+#ifdef SK_SUPPORT_LEGACY_DRAWFLTER
         fFilter = canvas->getDrawFilter();
+#else
+        fFilter = nullptr;
+#endif
         fPaint = &fOrigPaint;
         fSaveCount = canvas->getSaveCount();
         fTempLayerForImageFilter = false;
@@ -778,6 +782,7 @@
     dec_canvas();
 }
 
+#ifdef SK_SUPPORT_LEGACY_DRAWFLTER
 SkDrawFilter* SkCanvas::getDrawFilter() const {
     return fMCRec->fFilter;
 }
@@ -787,6 +792,7 @@
     SkRefCnt_SafeAssign(fMCRec->fFilter, filter);
     return filter;
 }
+#endif
 
 SkMetaData& SkCanvas::getMetaData() {
     // metadata users are rare, so we lazily allocate it. If that changes we