Add sRGB texture support.

Review URL: https://codereview.chromium.org/791823003
diff --git a/src/gpu/gl/GrGLDefines.h b/src/gpu/gl/GrGLDefines.h
index 0eb5149..fc44252 100644
--- a/src/gpu/gl/GrGLDefines.h
+++ b/src/gpu/gl/GrGLDefines.h
@@ -770,6 +770,8 @@
 #define GR_GL_FRAMEBUFFER_ATTACHMENT_TEXTURE_LEVEL         0x8CD2
 #define GR_GL_FRAMEBUFFER_ATTACHMENT_TEXTURE_CUBE_MAP_FACE 0x8CD3
 #define GR_GL_FRAMEBUFFER_ATTACHMENT_TEXTURE_LAYER         0x8CD4
+#define GR_GL_FRAMEBUFFER_ATTACHMENT_COLOR_ENCODING        0x8210
+#define GR_GL_FRAMEBUFFER_ATTACHMENT_COMPONENT_TYPE        0x8211
 #define GR_GL_FRAMEBUFFER_ATTACHMENT_RED_SIZE              0x8212
 #define GR_GL_FRAMEBUFFER_ATTACHMENT_GREEN_SIZE            0x8213
 #define GR_GL_FRAMEBUFFER_ATTACHMENT_BLUE_SIZE             0x8214