Add support for GL_ANGLE_texture_usage

Review URL: http://codereview.appspot.com/5478052/



git-svn-id: http://skia.googlecode.com/svn/trunk@2845 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/include/gpu/GrGLDefines.h b/include/gpu/GrGLDefines.h
index 4dc6278..6a57982 100644
--- a/include/gpu/GrGLDefines.h
+++ b/include/gpu/GrGLDefines.h
@@ -369,11 +369,15 @@
 #define GR_GL_NEAREST_MIPMAP_LINEAR          0x2702
 #define GR_GL_LINEAR_MIPMAP_LINEAR           0x2703
 
+/* TextureUsage */
+#define GR_GL_FRAMEBUFFER_ATTACHMENT         0x93A3
+
 /* TextureParameterName */
 #define GR_GL_TEXTURE_MAG_FILTER             0x2800
 #define GR_GL_TEXTURE_MIN_FILTER             0x2801
 #define GR_GL_TEXTURE_WRAP_S                 0x2802
 #define GR_GL_TEXTURE_WRAP_T                 0x2803
+#define GR_GL_TEXTURE_USAGE                  0x93A2
 
 /* TextureTarget */
 /*      GL_TEXTURE_2D */