Dynamically create stencil buffer when needed.

src/gpu/GrGpu.h

Index: src/gpu/GrGpu.h
diff --git a/src/gpu/GrGpu.h b/src/gpu/GrGpu.h
index a0950e001cffddce3fa8d93e21c7854cba815493..eb97b4fa08922c0f7b79aa74621b35f2c0c28102 100644
--- a/src/gpu/GrGpu.h
+++ b/src/gpu/GrGpu.h
@@ -405,6 +405,9 @@ public:
     void saveActiveTraceMarkers();
     void restoreActiveTraceMarkers();
 
+    // Given a rt, find or create a stencil buffer and attach it
+    bool attachStencilBufferToRenderTarget(GrRenderTarget* target);
+
 protected:
     // Functions used to map clip-respecting stencil tests into normal
     // stencil funcs supported by GPUs.
@@ -489,9 +492,6 @@ private:
     // clears target's entire stencil buffer to 0
     virtual void clearStencil(GrRenderTarget* target) = 0;
 
-    // Given a rt, find or create a stencil buffer and attach it
-    bool attachStencilBufferToRenderTarget(GrRenderTarget* target);
-
     virtual void didAddGpuTraceMarker() = 0;
     virtual void didRemoveGpuTraceMarker() = 0;