Add GLSL support for texelFetch

src/gpu/glsl/GrGLSLShaderBuilder.h

Index: src/gpu/glsl/GrGLSLShaderBuilder.h
diff --git a/src/gpu/glsl/GrGLSLShaderBuilder.h b/src/gpu/glsl/GrGLSLShaderBuilder.h
index 6f8bf68bab5a6f25b067b8f048c40f128a5570e8..c14df5391507a34cb6ea462d07877e658e056480 100644
--- a/src/gpu/glsl/GrGLSLShaderBuilder.h
+++ b/src/gpu/glsl/GrGLSLShaderBuilder.h
@@ -34,7 +34,7 @@ public:
                              const char* coordName,
                              GrSLType coordType = kVec2f_GrSLType) const;
 
-    /** Version of above that appends the result to the fragment shader code instead.*/
+    /** Version of above that appends the result to the shader code instead.*/
     void appendTextureLookup(const GrGLSLSampler&,
                              const char* coordName,
                              GrSLType coordType = kVec2f_GrSLType);
@@ -49,6 +49,14 @@ public:
                                         const char* coordName,
                                         GrSLType coordType = kVec2f_GrSLType);
 
+    /** Fetches an unfiltered texel from a sampler at integer coordinates. coordExpr must match the
+        dimensionality of the sampler and must be within the sampler's range. coordExpr is emitted
+        exactly once, so expressions like "idx++" are acceptable. */
+    void appendTexelFetch(SkString* out, const GrGLSLSampler&, const char* coordExpr) const;
+
+    /** Version of above that appends the result to the shader code instead.*/
+    void appendTexelFetch(const GrGLSLSampler&, const char* coordExpr);
+
     /**
     * Adds a #define directive to the top of the shader.
     */
@@ -175,6 +183,12 @@ protected:
 
     void compileAndAppendLayoutQualifiers();
 
+    /* Appends any swizzling we may need to get from some backend internal format to the format used
+     * in GrPixelConfig. If this is implemented by the GrGpu object, then swizzle will be rgba. For
+     * shader prettiness we omit the swizzle rather than appending ".rgba".
+     */
+    void appendTextureSwizzle(SkString* out, GrPixelConfig) const;
+
     void nextStage() {
         fShaderStrings.push_back();
         fCompilerStrings.push_back(this->code().c_str());