Don't track FB depth attachment in debug GL context

tools/gpu/gl/debug/GrFrameBufferObj.h

Index: tools/gpu/gl/debug/GrFrameBufferObj.h
diff --git a/tools/gpu/gl/debug/GrFrameBufferObj.h b/tools/gpu/gl/debug/GrFrameBufferObj.h
index 42a0effe072fb11cb9f1d5593bd69ac2b8c12a1f..0a45cf7b6b6ebc13778a65c539d849d76a13be19 100644
--- a/tools/gpu/gl/debug/GrFrameBufferObj.h
+++ b/tools/gpu/gl/debug/GrFrameBufferObj.h
@@ -23,13 +23,11 @@ public:
         : GrFakeRefObj()
         , fBound(false)
         , fColorBuffer(nullptr)
-        , fDepthBuffer(nullptr)
         , fStencilBuffer(nullptr) {
     }
 
     virtual ~GrFrameBufferObj() {
         fColorBuffer = nullptr;
-        fDepthBuffer = nullptr;
         fStencilBuffer = nullptr;
     }
 
@@ -40,16 +38,12 @@ public:
     void setColor(GrFBBindableObj *buffer);
     GrFBBindableObj *getColor()       { return fColorBuffer; }
 
-    void setDepth(GrFBBindableObj *buffer);
-    GrFBBindableObj *getDepth()       { return fDepthBuffer; }
-
     void setStencil(GrFBBindableObj *buffer);
     GrFBBindableObj *getStencil()     { return fStencilBuffer; }
 
     void deleteAction() override {
 
         setColor(nullptr);
-        setDepth(nullptr);
         setStencil(nullptr);
 
         this->INHERITED::deleteAction();
@@ -59,7 +53,6 @@ protected:
 private:
     bool fBound;        // is this frame buffer currently bound via "glBindFramebuffer"?
     GrFBBindableObj * fColorBuffer;
-    GrFBBindableObj * fDepthBuffer;
     GrFBBindableObj * fStencilBuffer;
 
     typedef GrFakeRefObj INHERITED;