Move some of the adding stencil attachment logic of Gpu and into Render Target.

src/gpu/GrRenderTarget.cpp

Index: src/gpu/GrRenderTarget.cpp
diff --git a/src/gpu/GrRenderTarget.cpp b/src/gpu/GrRenderTarget.cpp
index 5cb34e849aa1ed601fe908d7c201066aa554198d..0a362de6e90305a5bf24e21524bdced72a6ffcd0 100644
--- a/src/gpu/GrRenderTarget.cpp
+++ b/src/gpu/GrRenderTarget.cpp
@@ -72,12 +72,29 @@ void GrRenderTargetPriv::didAttachStencilAttachment(GrStencilAttachment* stencil
     SkRefCnt_SafeAssign(fRenderTarget->fStencilAttachment, stencilAttachment);
 }
 
-GrStencilAttachment* GrRenderTargetPriv::attachStencilAttachment() const {
+GrStencilAttachment* GrRenderTargetPriv::attachStencilAttachment() {
     if (fRenderTarget->fStencilAttachment) {
         return fRenderTarget->fStencilAttachment;
     }
     if (!fRenderTarget->wasDestroyed() && fRenderTarget->canAttemptStencilAttachment()) {
-        fRenderTarget->getGpu()->attachStencilAttachmentToRenderTarget(fRenderTarget);
+        bool newStencil = fRenderTarget->getGpu()->getStencilAttachment(
+            fRenderTarget, &fRenderTarget->fStencilAttachment);
+        if (!fRenderTarget->completeStencilAttachment()) {
+            SkSafeSetNull(fRenderTarget->fStencilAttachment);
+        } else {
+            if (newStencil) {
+                // Right now we're clearing the stencil attachment here after it is
+                // attached to an RT for the first time. When we start matching
+                // stencil buffers with smaller color targets this will no longer
+                // be correct because it won't be guaranteed to clear the entire
+                // sb.
+                // We used to clear down in the GL subclass using a special purpose
+                // FBO. But iOS doesn't allow a stencil-only FBO. It reports unsupported
+                // FBO status.
+                fRenderTarget->getGpu()->clearStencil(fRenderTarget); 
+            }
+        }
     }
     return fRenderTarget->fStencilAttachment;
 }
+