Rename SkCanvasDrawable to SkDrawable, and make public

 (patchset #2 id:20001 of https://codereview.chromium.org/903993002/)"

This reverts commit c4e87724920222a218f31b22612efc5b1ec0ed6c.

BUG=skia:
TBR=
NOTREECHECKS=True

Review URL: https://codereview.chromium.org/898343004
diff --git a/src/core/SkCanvas.cpp b/src/core/SkCanvas.cpp
index 055e673..ce99546 100644
--- a/src/core/SkCanvas.cpp
+++ b/src/core/SkCanvas.cpp
@@ -6,11 +6,11 @@
  */
 
 #include "SkCanvas.h"
-#include "SkCanvasDrawable.h"
 #include "SkCanvasPriv.h"
 #include "SkBitmapDevice.h"
 #include "SkDeviceImageFilterProxy.h"
 #include "SkDraw.h"
+#include "SkDrawable.h"
 #include "SkDrawFilter.h"
 #include "SkDrawLooper.h"
 #include "SkImage.h"
@@ -2293,13 +2293,13 @@
     LOOPER_END
 }
 
-void SkCanvas::EXPERIMENTAL_drawDrawable(SkCanvasDrawable* dr) {
+void SkCanvas::drawDrawable(SkDrawable* dr) {
     if (dr && !this->quickReject(dr->getBounds())) {
         this->onDrawDrawable(dr);
     }
 }
 
-void SkCanvas::onDrawDrawable(SkCanvasDrawable* dr) {
+void SkCanvas::onDrawDrawable(SkDrawable* dr) {
     dr->draw(this);
 }