Move some work from backend onClear to base class clear

src/gpu/gl/GrGLCaps.h

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #ifndef GrGLCaps_DEFINED
 #define GrGLCaps_DEFINED
@@ skipping 234 matching lines @@
     }
 
     /// Does ReadPixels support the provided format/type combo?
     bool readPixelsSupported(const GrGLInterface* intf,
                              GrGLenum format,
                              GrGLenum type,
                              GrGLenum currFboFormat) const;
 
     bool isCoreProfile() const { return fIsCoreProfile; }
 
-    bool fullClearIsFree() const { return fFullClearIsFree; }
-
     bool bindFragDataLocationSupport() const { return fBindFragDataLocationSupport; }
 
     /**
      * Is there support for enabling/disabling sRGB writes for sRGB-capable color attachments?
      * If false this does not mean sRGB is not supported but rather that if it is supported
      * it cannot be turned off for configs that support it.
      */
     bool srgbWriteControl() const { return fSRGBWriteControl; }
 
     /**
@@ skipping 106 matching lines @@
     bool fTwoFormatLimit : 1;
     bool fFragCoordsConventionSupport : 1;
     bool fVertexArrayObjectSupport : 1;
     bool fInstancedDrawingSupport : 1;
     bool fDirectStateAccessSupport : 1;
     bool fDebugSupport : 1;
     bool fES2CompatibilitySupport : 1;
     bool fMultisampleDisableSupport : 1;
     bool fUseNonVBOVertexAndIndexDynamicData : 1;
     bool fIsCoreProfile : 1;
-    bool fFullClearIsFree : 1;
     bool fBindFragDataLocationSupport : 1;
     bool fSRGBWriteControl : 1;
     bool fRGBA8888PixelsOpsAreSlow : 1;
     bool fPartialFBOReadIsSlow : 1;
 
     struct ReadPixelsSupportedFormat {
         GrGLenum fFormat;
         GrGLenum fType;
         GrGLenum fFboFormat;
 
         bool operator==(const ReadPixelsSupportedFormat& rhs) const {
             return fFormat    == rhs.fFormat
                 && fType      == rhs.fType
                 && fFboFormat == rhs.fFboFormat;
         }
     };
     mutable SkTHashMap<ReadPixelsSupportedFormat, bool> fReadPixelsSupportedCache;
 
     typedef GrCaps INHERITED;
 };
 
 #endif