Add blend optimization helpers and use to convert rect draws to clears.

src/gpu/GrDrawState.h

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrDrawState_DEFINED
 #define GrDrawState_DEFINED
 
 #include "GrBackendEffectFactory.h"
+#include "GrBlend.h"
 #include "GrColor.h"
 #include "GrEffectStage.h"
 #include "GrPaint.h"
 #include "GrPoint.h"
 #include "GrRefCnt.h"
 #include "GrRenderTarget.h"
 #include "GrStencil.h"
 #include "GrTemplates.h"
 #include "GrTexture.h"
 #include "GrTypesPriv.h"
@@ skipping 440 matching lines @@
      *   color, and D' is the new destination color that will be written. sat()
      *   is the saturation function.
      *
      * @param srcCoef coefficient applied to the src color.
      * @param dstCoef coefficient applied to the dst color.
      */
     void setBlendFunc(GrBlendCoeff srcCoeff, GrBlendCoeff dstCoeff) {
         fCommon.fSrcBlend = srcCoeff;
         fCommon.fDstBlend = dstCoeff;
     #if GR_DEBUG
-        switch (dstCoeff) {
-        case kDC_GrBlendCoeff:
-        case kIDC_GrBlendCoeff:
-        case kDA_GrBlendCoeff:
-        case kIDA_GrBlendCoeff:
-            GrPrintf("Unexpected dst blend coeff. Won't work correctly with"
-                     "coverage stages.\n");
-            break;
-        default:
-            break;
+        if (GrBlendCoeffRefsDst(dstCoeff)) {
+            GrPrintf("Unexpected dst blend coeff. Won't work correctly with coverage stages.\n");
         }
-        switch (srcCoeff) {
-        case kSC_GrBlendCoeff:
-        case kISC_GrBlendCoeff:
-        case kSA_GrBlendCoeff:
-        case kISA_GrBlendCoeff:
-            GrPrintf("Unexpected src blend coeff. Won't work correctly with"
-                     "coverage stages.\n");
-            break;
-        default:
-            break;
+        if (GrBlendCoeffRefsSrc(srcCoeff)) {
+            GrPrintf("Unexpected src blend coeff. Won't work correctly with coverage stages.\n");
         }
     #endif
     }
 
     GrBlendCoeff getSrcBlendCoeff() const { return fCommon.fSrcBlend; }
     GrBlendCoeff getDstBlendCoeff() const { return fCommon.fDstBlend; }
 
     void getDstBlendCoeff(GrBlendCoeff* srcBlendCoeff,
                           GrBlendCoeff* dstBlendCoeff) const {
         *srcBlendCoeff = fCommon.fSrcBlend;
@@ skipping 588 matching lines @@
      *  @param count      the number of attributes being set, limited to kMaxVertexAttribCnt.
      */
     void setVertexAttribs(const GrVertexAttrib attribs[], int count);
 
     typedef GrRefCnt INHERITED;
 };
 
 GR_MAKE_BITFIELD_OPS(GrDrawState::BlendOptFlags);
 
 #endif