Implement support for KHR_blend_equation_advanced

src/gpu/gl/GrGLCaps.h

Index: src/gpu/gl/GrGLCaps.h
diff --git a/src/gpu/gl/GrGLCaps.h b/src/gpu/gl/GrGLCaps.h
index 13ba3863b1228efc806a0da20e7c0f0fee30604b..5f98b7661c9cf4dae0d5d0fd0ce93e506d1a7527 100644
--- a/src/gpu/gl/GrGLCaps.h
+++ b/src/gpu/gl/GrGLCaps.h
@@ -380,6 +380,19 @@ public:
     SK_DECLARE_INST_COUNT(GrGLSLCaps)
 
     /**
+    * Indicates how GLSL must interact with advanced blend equations. The KHR extension requires
+    * special layout qualifiers in the fragment shader.
+    */
+    enum AdvancedBlendEqnInteraction {
+        kNotSupported_AdvancedBlendEqnInteraction,         //<! No advanced blend equation support
+        kAutomatic_AdvancedBlendEqnInteraction,            //<! No interaction required
+        kMustEnable_AdvancedBlendEqnInteraction,           //<! Blanket qualifier for all equations
+        kMustEnableSeparately_AdvancedBlendEqnInteraction, //<! Separate qualifiers per equation
+
+        kLast_AdvancedBlendEqnInteraction = kMustEnableSeparately_AdvancedBlendEqnInteraction
+    };
+
+    /**
      * Creates a GrGLSLCaps that advertises no support for any extensions,
      * formats, etc. Call init to initialize from a GrGLContextInfo.
      */
@@ -399,7 +412,7 @@ public:
      * Initializes the GrGLSLCaps to the set of features supported in the current
      * OpenGL context accessible via ctxInfo.
      */
-    bool init(const GrGLContextInfo& ctxInfo, const GrGLInterface* glInterface);
+    bool init(const GrGLContextInfo&, const GrGLInterface*, const GrGLCaps&);
 
     /**
      * Some helper functions for encapsulating various extensions to read FB Buffer on openglES
@@ -416,6 +429,14 @@ public:
 
     bool dropsTileOnZeroDivide() const { return fDropsTileOnZeroDivide; }
 
+    AdvancedBlendEqnInteraction advancedBlendEqnInteraction() const {
+        return fAdvancedBlendEqnInteraction;
+    }
+
+    bool mustEnableAdvancedBlendEquations() const {
+        return fAdvancedBlendEqnInteraction >= kMustEnable_AdvancedBlendEqnInteraction;
+    }
+
     /**
     * Returns a string containing the caps info.
     */
@@ -432,6 +453,8 @@ private:
     const char* fFBFetchColorName;
     const char* fFBFetchExtensionString;
 
+    AdvancedBlendEqnInteraction fAdvancedBlendEqnInteraction;
+
     typedef GrShaderCaps INHERITED;
 };