Swap render target instead of creating a new gpu device for surface copy-on-write

src/image/SkSurface_Gpu.cpp

Index: src/image/SkSurface_Gpu.cpp
diff --git a/src/image/SkSurface_Gpu.cpp b/src/image/SkSurface_Gpu.cpp
index a1c31f31379ad022735e69dd5a64636f6149fca4..b94e4e30bd07f7a097a94a151a06b9558329476b 100644
--- a/src/image/SkSurface_Gpu.cpp
+++ b/src/image/SkSurface_Gpu.cpp
@@ -7,7 +7,6 @@
 
 #include "SkSurface_Gpu.h"
 
-#include "GrGpuResourcePriv.h"
 #include "SkCanvas.h"
 #include "SkGpuDevice.h"
 #include "SkImage_Base.h"
@@ -24,7 +23,7 @@ SkSurface_Gpu::SkSurface_Gpu(SkGpuDevice* device)
 }
 
 SkSurface_Gpu::~SkSurface_Gpu() {
-    SkSafeUnref(fDevice);
+    fDevice->unref();
 }
 
 SkCanvas* SkSurface_Gpu::onNewCanvas() {
@@ -59,8 +58,8 @@ void SkSurface_Gpu::onDraw(SkCanvas* canvas, SkScalar x, SkScalar y,
     canvas->drawBitmap(fDevice->accessBitmap(false), x, y, paint);
 }
 
-// Create a new SkGpuDevice and, if necessary, copy the contents of the old
-// device into it. Note that this flushes the SkGpuDevice but
+// Create a new render target and, if necessary, copy the contents of the old
+// render target into it. Note that this flushes the SkGpuDevice but
 // doesn't force an OpenGL flush.
 void SkSurface_Gpu::onCopyOnWrite(ContentChangeMode mode) {
     GrRenderTarget* rt = fDevice->accessRenderTarget();
@@ -69,22 +68,7 @@ void SkSurface_Gpu::onCopyOnWrite(ContentChangeMode mode) {
     SkImage* image = this->getCachedImage(kNo_Budgeted);
     SkASSERT(image);
     if (rt->asTexture() == SkTextureImageGetTexture(image)) {
-        GrRenderTarget* oldRT = this->fDevice->accessRenderTarget();
-        SkSurface::Budgeted budgeted = oldRT->resourcePriv().isBudgeted() ? kYes_Budgeted :
-                                                                            kNo_Budgeted;
-        SkAutoTUnref<SkGpuDevice> newDevice(
-            SkGpuDevice::Create(oldRT->getContext(), budgeted, fDevice->imageInfo(),
-                                oldRT->numSamples(), &this->props(), 0));
-        if (kRetain_ContentChangeMode == mode && !oldRT->wasDestroyed() && newDevice) {
-            oldRT->getContext()->copySurface(newDevice->accessRenderTarget(), oldRT);
-        }
-
-        SkASSERT(this->getCachedCanvas());
-        SkASSERT(this->getCachedCanvas()->getDevice() == fDevice);
-
-        this->getCachedCanvas()->setRootDevice(newDevice);
-        SkRefCnt_SafeAssign(fDevice, newDevice.get());
-
+        this->fDevice->replaceRenderTarget(SkSurface::kRetain_ContentChangeMode == mode);
         SkTextureImageApplyBudgetedDecision(image);
     } else if (kDiscard_ContentChangeMode == mode) {
         this->SkSurface_Gpu::onDiscard();