Remove unused member variables in GrGLProgram

BUG=skia:

Review URL: https://codereview.chromium.org/1416523003
diff --git a/src/gpu/gl/GrGLProgram.cpp b/src/gpu/gl/GrGLProgram.cpp
index 9138daf..7514106 100644
--- a/src/gpu/gl/GrGLProgram.cpp
+++ b/src/gpu/gl/GrGLProgram.cpp
@@ -35,10 +35,7 @@
                          GrGLInstalledXferProc* xferProcessor,
                          GrGLInstalledFragProcs* fragmentProcessors,
                          SkTArray<UniformHandle>* passSamplerUniforms)
-    : fColor(GrColor_ILLEGAL)
-    , fCoverage(0)
-    , fDstTextureUnit(-1)
-    , fBuiltinUniformHandles(builtinUniforms)
+    : fBuiltinUniformHandles(builtinUniforms)
     , fProgramID(programID)
     , fGeometryProcessor(geometryProcessor)
     , fXferProcessor(xferProcessor)
diff --git a/src/gpu/gl/GrGLProgram.h b/src/gpu/gl/GrGLProgram.h
index 9381a6c..9c5ab73 100644
--- a/src/gpu/gl/GrGLProgram.h
+++ b/src/gpu/gl/GrGLProgram.h
@@ -125,9 +125,6 @@
 
     // these reflect the current values of uniforms (GL uniform values travel with program)
     RenderTargetState fRenderTargetState;
-    GrColor fColor;
-    uint8_t fCoverage;
-    int fDstTextureUnit;
     BuiltinUniformHandles fBuiltinUniformHandles;
     GrGLuint fProgramID;