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

src/gpu/SkGpuDevice.cpp

Index: src/gpu/SkGpuDevice.cpp
diff --git a/src/gpu/SkGpuDevice.cpp b/src/gpu/SkGpuDevice.cpp
index 8912851d8f369c88a9b36aeb7d281c8b2490c690..7b881d60a298e31005aefd375d6428b55df6b70f 100644
--- a/src/gpu/SkGpuDevice.cpp
+++ b/src/gpu/SkGpuDevice.cpp
@@ -38,6 +38,7 @@
 #include "SkRRect.h"
 #include "SkStroke.h"
 #include "SkSurface.h"
+#include "SkSurface_Gpu.h"
 #include "SkTLazy.h"
 #include "SkUtils.h"
 #include "SkVertState.h"
@@ -165,9 +166,8 @@ SkGpuDevice::SkGpuDevice(GrRenderTarget* rt, const SkSurfaceProps* props, unsign
     fTextContext = fContext->createTextContext(fRenderTarget, this->getLeakyProperties(), useDFT);
 }
 
-SkGpuDevice* SkGpuDevice::Create(GrContext* context, SkSurface::Budgeted budgeted,
-                                 const SkImageInfo& origInfo, int sampleCount,
-                                 const SkSurfaceProps* props, unsigned flags) {
+GrRenderTarget* SkGpuDevice::CreateRenderTarget(GrContext* context, SkSurface::Budgeted budgeted,
+                                                const SkImageInfo& origInfo, int sampleCount) {
     if (kUnknown_SkColorType == origInfo.colorType() ||
         origInfo.width() < 0 || origInfo.height() < 0) {
         return NULL;
@@ -196,13 +196,24 @@ SkGpuDevice* SkGpuDevice::Create(GrContext* context, SkSurface::Budgeted budgete
     desc.fHeight = info.height();
     desc.fConfig = SkImageInfo2GrPixelConfig(info);
     desc.fSampleCnt = sampleCount;
+    GrTexture* texture = context->createTexture(desc, SkToBool(budgeted), NULL, 0);
+    if (NULL == texture) {
+        return NULL;
+    }
+    SkASSERT(NULL != texture->asRenderTarget());
+    return texture->asRenderTarget();
+}
 
-    SkAutoTUnref<GrTexture> texture(context->createTexture(desc, SkToBool(budgeted), NULL, 0));
-    if (!texture) {
+SkGpuDevice* SkGpuDevice::Create(GrContext* context, SkSurface::Budgeted budgeted,
+                                 const SkImageInfo& info, int sampleCount,
+                                 const SkSurfaceProps* props, unsigned flags) {
+
+    SkAutoTUnref<GrRenderTarget> rt(CreateRenderTarget(context, budgeted, info, sampleCount));
+    if (!rt) {
         return NULL;
     }
 
-    return SkNEW_ARGS(SkGpuDevice, (texture->asRenderTarget(), props, flags));
+    return SkNEW_ARGS(SkGpuDevice, (rt, props, flags));
 }
 
 SkGpuDevice::~SkGpuDevice() {
@@ -311,6 +322,18 @@ void SkGpuDevice::clearAll() {
     fNeedClear = false;
 }
 
+void SkGpuDevice::swapRenderTarget(GrRenderTarget* newRenderTarget) {
+    SkASSERT(!fNeedClear);
+    if (fContext->getRenderTarget() == fRenderTarget) {
+        fContext->setRenderTarget(NULL);
+    }
+    SkRefCnt_SafeAssign(fRenderTarget, newRenderTarget);
+    SkASSERT(newRenderTarget->surfacePriv().info() == fLegacyBitmap.info());
+    SkPixelRef* pr = SkNEW_ARGS(SkGrPixelRef, (newRenderTarget->surfacePriv().info(),
+                                               newRenderTarget));
+    fLegacyBitmap.setPixelRef(pr)->unref();
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 
 SK_COMPILE_ASSERT(SkShader::kNone_BitmapType == 0, shader_type_mismatch);