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

include/gpu/GrPaint.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 GrPaint_DEFINED
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      */
     void reset() {
         this->resetBlend();
         this->resetOptions();
         this->resetColor();
         this->resetCoverage();
         this->resetStages();
         this->resetColorFilter();
     }
 
+    /**
+     * Determines whether the drawing with this paint is opaque with respect to both color blending
+     * and fractional coverage. It does not consider whether AA has been enabled on the paint or
+     * not. Depending upon whether multisampling or coverage-based AA is in use, AA may make the
+     * result only apply to the interior of primitives.
+     *
+     */
+    bool isOpaque() const;
+
+    /**
+     * Returns true if isOpaque would return true and the paint represents a solid constant color
+     * draw. If the result is true, constantColor will be updated to contain the constant color.
+     */
+    bool isOpaqueAndConstantColor(GrColor* constantColor) const;
+
 private:
+
+    /**
+     * Helper for isOpaque and isOpaqueAndConstantColor.
+     */
+    bool getOpaqueAndKnownColor(GrColor* solidColor, uint32_t* solidColorKnownComponents) const;
+
     /**
      * Called when the source coord system from which geometry is rendered changes. It ensures that
      * the local coordinates seen by effects remains unchanged. oldToNew gives the transformation
      * from the previous coord system to the new coord system.
      */
     void localCoordChange(const SkMatrix& oldToNew) {
         for (int i = 0; i < fColorStages.count(); ++i) {
             fColorStages[i].localCoordChange(oldToNew);
         }
         for (int i = 0; i < fCoverageStages.count(); ++i) {
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         fCoverage = 0xff;
     }
 
     void resetStages() {
         fColorStages.reset();
         fCoverageStages.reset();
     }
 };
 
 #endif