Revert of Revert of Move DstCopy on gpu into the GrXferProcessor.

src/gpu/GrDrawTarget.cpp

Index: src/gpu/GrDrawTarget.cpp
diff --git a/src/gpu/GrDrawTarget.cpp b/src/gpu/GrDrawTarget.cpp
index b89d70ea2be724e2a8fb5bff5e1f6364efd5f31d..111f455883e269d1b77838215119ef8f1f09a592 100644
--- a/src/gpu/GrDrawTarget.cpp
+++ b/src/gpu/GrDrawTarget.cpp
@@ -384,15 +384,15 @@
     return true;
 }
 
-bool GrDrawTarget::setupDstReadIfNecessary(GrPipelineBuilder* pipelineBuilder,
+bool GrDrawTarget::setupDstReadIfNecessary(const GrPipelineBuilder& pipelineBuilder,
                                            GrDeviceCoordTexture* dstCopy,
                                            const SkRect* drawBounds) {
-    if (this->caps()->dstReadInShaderSupport() || !pipelineBuilder->willEffectReadDstColor()) {
+    if (!pipelineBuilder.willXPNeedDstCopy(*this->caps())) {
         return true;
     }
     SkIRect copyRect;
     const GrClipData* clip = this->getClip();
-    GrRenderTarget* rt = pipelineBuilder->getRenderTarget();
+    GrRenderTarget* rt = pipelineBuilder.getRenderTarget();
     clip->getConservativeBounds(rt, &copyRect);
 
     if (drawBounds) {
@@ -470,14 +470,9 @@
             info.setDevBounds(*devBounds);
         }
 
-        // TODO: We should continue with incorrect blending.
-        GrDeviceCoordTexture dstCopy;
-        if (!this->setupDstReadIfNecessary(pipelineBuilder, &dstCopy, devBounds)) {
-            return;
-        }
         this->setDrawBuffers(&info, gp->getVertexStride());
 
-        this->onDraw(*pipelineBuilder, gp, info, scissorState, dstCopy.texture() ? &dstCopy : NULL);
+        this->onDraw(*pipelineBuilder, gp, info, scissorState);
     }
 }
 
@@ -514,15 +509,9 @@
             info.setDevBounds(*devBounds);
         }
 
-        // TODO: We should continue with incorrect blending.
-        GrDeviceCoordTexture dstCopy;
-        if (!this->setupDstReadIfNecessary(pipelineBuilder, &dstCopy, devBounds)) {
-            return;
-        }
-
         this->setDrawBuffers(&info, gp->getVertexStride());
 
-        this->onDraw(*pipelineBuilder, gp, info, scissorState, dstCopy.texture() ? &dstCopy : NULL);
+        this->onDraw(*pipelineBuilder, gp, info, scissorState);
     }
 }
 
@@ -541,12 +530,7 @@
         return;
     }
 
-    GrDeviceCoordTexture dstCopy;
-    if (!this->setupDstReadIfNecessary(pipelineBuilder, &dstCopy, devBounds)) {
-        return;
-    }
-
-    this->onDrawBatch(batch, *pipelineBuilder, scissorState, dstCopy.texture() ? &dstCopy : NULL);
+    this->onDrawBatch(batch, *pipelineBuilder, scissorState, devBounds);
 }
 
 static const GrStencilSettings& winding_path_stencil_settings() {
@@ -636,13 +620,8 @@
                                             pipelineBuilder->getRenderTarget()->getStencilBuffer(),
                                             &stencilSettings);
 
-    GrDeviceCoordTexture dstCopy;
-    if (!this->setupDstReadIfNecessary(pipelineBuilder, &dstCopy, &devBounds)) {
-        return;
-    }
-
     this->onDrawPath(*pipelineBuilder, pathProc, path, scissorState, stencilSettings,
-                     dstCopy.texture() ? &dstCopy : NULL);
+                     &devBounds);
 }
 
 void GrDrawTarget::drawPaths(GrPipelineBuilder* pipelineBuilder,
@@ -676,18 +655,12 @@
                                             pipelineBuilder->getRenderTarget()->getStencilBuffer(),
                                             &stencilSettings);
 
-    // Don't compute a bounding box for setupDstReadIfNecessary(), we'll opt
+    // Don't compute a bounding box for dst copy texture, we'll opt
     // instead for it to just copy the entire dst. Realistically this is a moot
     // point, because any context that supports NV_path_rendering will also
     // support NV_blend_equation_advanced.
-    GrDeviceCoordTexture dstCopy;
-    if (!this->setupDstReadIfNecessary(pipelineBuilder, &dstCopy, NULL)) {
-        return;
-    }
-
     this->onDrawPaths(*pipelineBuilder, pathProc, pathRange, indices, indexType, transformValues,
-                      transformType, count, scissorState, stencilSettings,
-                      dstCopy.texture() ? &dstCopy : NULL);
+                      transformType, count, scissorState, stencilSettings, NULL);
 }
 
 void GrDrawTarget::clear(const SkIRect* rect,
@@ -793,12 +766,6 @@
         info.setDevBounds(*devBounds);
     }
 
-    // TODO: We should continue with incorrect blending.
-    GrDeviceCoordTexture dstCopy;
-    if (!this->setupDstReadIfNecessary(pipelineBuilder, &dstCopy, devBounds)) {
-        return;
-    }
-
     while (instanceCount) {
         info.fInstanceCount = SkTMin(instanceCount, maxInstancesPerDraw);
         info.fVertexCount = info.fInstanceCount * verticesPerInstance;
@@ -812,8 +779,7 @@
                             info.fVertexCount,
                             info.fIndexCount)) {
             this->setDrawBuffers(&info, gp->getVertexStride());
-            this->onDraw(*pipelineBuilder, gp, info, scissorState,
-                         dstCopy.texture() ? &dstCopy : NULL);
+            this->onDraw(*pipelineBuilder, gp, info, scissorState);
         }
         info.fStartVertex += info.fVertexCount;
         instanceCount -= info.fInstanceCount;