Blur shader performance optimizations

- removed mipmap in favor of fbo approach
- bell curve computation outside of shade
- type casting optimizations
- pre-computation of shader variables
- increased UV precision to remove scaling artifacts
- move final copy operation to a blit

Test: visual
Test: systrace
Test: SurfaceFlinger_test
Fixes: 148292484
Change-Id: I2ad38cde837b090cadbadbb79b941dc0524948a4
diff --git a/libs/renderengine/gl/GLFramebuffer.h b/libs/renderengine/gl/GLFramebuffer.h
index 668685a..69102d6 100644
--- a/libs/renderengine/gl/GLFramebuffer.h
+++ b/libs/renderengine/gl/GLFramebuffer.h
@@ -48,6 +48,8 @@
     int32_t getBufferWidth() const { return mBufferWidth; }
     GLenum getStatus() const { return mStatus; }
     void bind() const;
+    void bindAsReadBuffer() const;
+    void bindAsDrawBuffer() const;
     void unbind() const;
 
 private: