Reduce number of GL calls when drawing with shaders.

Change-Id: I27aca9f6d381d5c7e363d90a93225d185f2ff4e3
diff --git a/libs/hwui/SkiaShader.h b/libs/hwui/SkiaShader.h
index 1d884ab..6702129 100644
--- a/libs/hwui/SkiaShader.h
+++ b/libs/hwui/SkiaShader.h
@@ -97,7 +97,11 @@
     void computeScreenSpaceMatrix(mat4& screenSpace, const mat4& modelView);
 
 protected:
-    inline void bindTexture(Texture* texture, GLenum wrapS, GLenum wrapT, GLuint textureUnit);
+    /**
+     * The appropriate texture unit must have been activated prior to invoking
+     * this method.
+     */
+    inline void bindTexture(Texture* texture, GLenum wrapS, GLenum wrapT);
 
     Type mType;
     SkShader* mKey;