Don't attempt mixed samples on "borrowed" render targets

Bug: skia:9231
Change-Id: I55809299c34bb835c2d3437b31dab318572a948d
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/225165
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>

Author: csmartdalton86

src/gpu/GrRenderTargetProxy.cpp

@@ -77,6 +77,15 @@ bool GrRenderTargetProxy::instantiate(GrResourceProvider* resourceProvider) {
     return true;
 }
 
+bool GrRenderTargetProxy::canChangeStencilAttachment() const {
+    if (!fTarget) {
+        // If we aren't instantiated, then we definitely are an internal render target. Ganesh is
+        // free to change stencil attachments on internal render targets.
+        return true;
+    }
+    return fTarget->asRenderTarget()->canAttemptStencilAttachment();
+}
+
 sk_sp<GrSurface> GrRenderTargetProxy::createSurface(GrResourceProvider* resourceProvider) const {
     static constexpr GrSurfaceDescFlags kDescFlags = kRenderTarget_GrSurfaceFlag;
 

src/gpu/GrRenderTargetProxy.h

@@ -29,9 +29,9 @@ class GrRenderTargetProxy : virtual public GrSurfaceProxy {
     bool instantiate(GrResourceProvider*) override;
 
     bool canUseMixedSamples(const GrCaps& caps) const {
-        // TODO: Is this a wrapped external RT? Is GrBackendObjectOwnership available?
         return caps.mixedSamplesSupport() && !this->glRTFBOIDIs0() &&
-               caps.internalMultisampleCount(this->config()) > 0;
+               caps.internalMultisampleCount(this->config()) > 0 &&
+               this->canChangeStencilAttachment();
     }
 
     /*
@@ -112,7 +112,7 @@ class GrRenderTargetProxy : virtual public GrSurfaceProxy {
     bool glRTFBOIDIs0() const {
         return fSurfaceFlags & GrInternalSurfaceFlags::kGLRTFBOIDIs0;
     }
-
+    bool canChangeStencilAttachment() const;
 
     size_t onUninstantiatedGpuMemorySize() const override;
     SkDEBUGCODE(void onValidateSurface(const GrSurface*) override;)

src/gpu/GrResourceProvider.cpp

@@ -418,7 +418,11 @@ bool GrResourceProvider::attachStencilAttachment(GrRenderTarget* rt, int minSten
         }
         rt->renderTargetPriv().attachStencilAttachment(std::move(stencil));
     }
-    return SkToBool(rt->renderTargetPriv().getStencilAttachment());
+
+    if (GrStencilAttachment* stencil = rt->renderTargetPriv().getStencilAttachment()) {
+        return stencil->numSamples() >= minStencilSampleCount;
+    }
+    return false;
 }
 
 sk_sp<GrRenderTarget> GrResourceProvider::wrapBackendTextureAsRenderTarget(