Revert "Change SkCanvas to *not* inherit from SkRefCnt"

This reverts commit 824075071885b6b741c141cbe2134d8345d34589.

Reason for revert: Breaking WebView (chromium:663959)

Original change's description:
> Change SkCanvas to *not* inherit from SkRefCnt
> 
> Definitely tricky for classes like SkNWayCanvas, where the caller (today)
> need not pay attention to ownership of the canvases it gave the NWay
> (after this CL, the caller *must* managed ownership)
> 
> BUG=skia:
> 
> GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=4441
> 
> DOCS_PREVIEW= https://skia.org/?cl=4441
> 
> Change-Id: Ib1ac07a3cdf0686d78e7aaa4735d45cc90bea081
> Reviewed-on: https://skia-review.googlesource.com/4441
> Commit-Queue: Mike Reed <reed@google.com>
> Reviewed-by: Florin Malita <fmalita@chromium.org>
> Reviewed-by: Robert Phillips <robertphillips@google.com>
> 

TBR=djsollen@google.com,mtklein@google.com,halcanary@google.com,robertphillips@google.com,fmalita@chromium.org,fmalita@google.com,reed@google.com,reviews@skia.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Change-Id: I5e3b3e876b7d2c09833cf841801321033b6b968b
Reviewed-on: https://skia-review.googlesource.com/4687
Commit-Queue: Heather Miller <hcm@google.com>
Reviewed-by: Heather Miller <hcm@google.com>

2 files changed, 7 insertions, 4 deletions

diff --git a/src/image/SkSurface.cpp b/src/image/SkSurface.cpp
index 3d6670f169..38bab9e32f 100644
--- a/src/image/SkSurface.cpp
+++ b/src/image/SkSurface.cpp
@@ -58,12 +58,14 @@ SkSurfaceProps::SkSurfaceProps(const SkSurfaceProps& other)
 SkSurface_Base::SkSurface_Base(int width, int height, const SkSurfaceProps* props)
     : INHERITED(width, height, props)
 {
+    fCachedCanvas = nullptr;
     fCachedImage = nullptr;
 }
 
 SkSurface_Base::SkSurface_Base(const SkImageInfo& info, const SkSurfaceProps* props)
     : INHERITED(info, props)
 {
+    fCachedCanvas = nullptr;
     fCachedImage = nullptr;
 }
 
@@ -74,6 +76,7 @@ SkSurface_Base::~SkSurface_Base() {
     }
 
     SkSafeUnref(fCachedImage);
+    SkSafeUnref(fCachedCanvas);
 }
 
 void SkSurface_Base::onDraw(SkCanvas* canvas, SkScalar x, SkScalar y, const SkPaint* paint) {
diff --git a/src/image/SkSurface_Base.h b/src/image/SkSurface_Base.h
index a8c1d8f0a4..8351bb87e6 100644
--- a/src/image/SkSurface_Base.h
+++ b/src/image/SkSurface_Base.h
@@ -89,8 +89,8 @@ public:
     uint32_t newGenerationID();
 
 private:
-    std::unique_ptr<SkCanvas>   fCachedCanvas;
-    SkImage*                    fCachedImage;
+    SkCanvas*   fCachedCanvas;
+    SkImage*    fCachedImage;
 
     void aboutToDraw(ContentChangeMode mode);
 
@@ -106,12 +106,12 @@ private:
 
 SkCanvas* SkSurface_Base::getCachedCanvas() {
     if (nullptr == fCachedCanvas) {
-        fCachedCanvas = std::unique_ptr<SkCanvas>(this->onNewCanvas());
+        fCachedCanvas = this->onNewCanvas();
         if (fCachedCanvas) {
             fCachedCanvas->setSurfaceBase(this);
         }
     }
-    return fCachedCanvas.get();
+    return fCachedCanvas;
 }
 
 sk_sp<SkImage> SkSurface_Base::refCachedImage(SkBudgeted budgeted, ForceUnique unique) {